I believe the reason red leader didnt go for a 2nd was that although the xwings have a capacity of 6 (2 at once) - so in other words 3 shots they were not fully loaded. Not only did this make them faster but it was not their purpose to destroy the deathstar so there was no point in giving them more. THe Ywings were full on torps afterall.

Red Leader didn't go for another run because he was a distance from the port after pulling up...

...and, uh, he got blowed up like a n00ber by Vader and impacted on the surface.

Owned.

The Y-wing has superior targeting capability to the X-wing. Partly due to it's secondary role as a light bomber. When the the Y-wing's targeting cpu and short range sensor systems are used in tandem with the long range sensors, it offers slightly better targeting accuracy than the X-wing. One reason why Y-wings were the primary attack craft at the Battle of Yavin. Dutch (Gold Leader), Tiree (Gold Two) and Pops (Gold Five) were able to identify, mark and lock the exhaust port in their targeting computers on their approach while Garvin, Luke and their wingmen were not. Garvin's torpedo volley had just barely missed the exhaust port. That being the case, it is evident that Dutch would have had no problem hitting the port had he gotten in range. Unfortunately he and his wingmen mad some very bad decisions on their approach. For one thing they had transfered all power to the deflector shield systems, effectively robbing a major portion of energy from the engines and vastly reducing their potential max speed. In addition, Dutch was unable to take effective evasive action without risking colliding with Pops due to him crowding his flight path. Both of them were killed as a result. What they should have done is transfer all power to the engines, increase speed full throttle and angle their deflector shields double back. Tiree and Pops should have stayed back far enough to cover him and have their ion cannons fixed dead aft for any possible pursuers. Essentially what Luke, Biggs and Wedge did, which was only logical. An even better solution would be to have Tiree and Pops piloting BTL-S3 Y-wings (two seater model) with two additional rebel pilots as gunners.

X-WING SPECS:

Vessel type: T-65 (X-wing) Starfighter
Designer/Manufacturer: Incom
Combat designation: Space Superiority Fighter
Crew: One pilot
                     One astromech droid
Power system: Nolvadex 04-Z cryogenic power cells and
                                     Ionazation reactor
Propulsion system: Four Incom 4j.4 fusial thrust engines (rated at 300KTU)
Flight control system: Torplex Rq8.Y flight control avionics package
Maneuverability rating: 75 DPF
Navigation: One astromech droid (usually a R2 unit)
                                           (carried in a patch-in cradle behind the cockpit)
Hyperdrive: Incom GBk-585 motivator drive unit
Sensor systems: Fabritech ANS-5d unit with
                                        LR Phased Tachyon Detection Array (PA-9r)
                                        SR Primary threat Analysis Grid (PG-7u)
Targeting computer: Fabritech Anq 3.6 tracking computer with
                                              IN-344-B "Sightline" holographic imaging system     
Weapons: Four Taim & Bak IX4 laser cannons
                                     (single fire or fire-linked)
                            Two Krupx MG7 proton torpedo launchers
                                      (three torpedoes each)
Defense: Forward/rear projecting Chempat shields
                                      (rated at 50SBD)
                        Titanium alloy hull (rated at 20 RU)

Excellent! But don't forget...

Maximum Sublight Speed: 80 MGLT
Maximum Acceleration: 3,700 Gs
Maximum Atmospheric Speed: 1,050 KPH/652 MPH
Hyperspace Capability: Class 1
Alternate Laser Cannon Assembly: Four Taim & Bak KX9 laser cannons
Defenses: Forward/Rear Projecting Chempat "Defender" deflector shield system

There were 22 X-wings and 8 Y-wings that assaulted the first Death Star at the Battle of Yavin. The Rebellion was hard pressed to find adequate resources to properly equip themselves for Imperial engagements. Funds were extremely limited. That being the case, many rebel fighters were not equiped with a full warhead capacity when in engaging Imperial forces. Luke's X-wing was only equipped with one volley of proton torpedoes (two torpedoes) as was Garvin's (Red Leader).

B-wing Default Weapon Configuration:
Two Gyhril 72 twin auto-blasters
One Gyrhil R-9X Laser Cannon
Three ArMek SW-7a ion cannons (fire-linked only)
Two Krupx MG9 proton torpedo launchers (6 torpedoes each)

A good word of advice for you guys. Do not quote Wikipedia/Wookiepedia or the X-wing/Tie Fighter sims for accurate Star Wars lore and technical information. The X-wing and TIE sims were fantastic games, but the technical specifications and descriptions of the craft and weaponry were heavily inaccurate. Which is a definate "no, no" when it comes to a simulator. Wikipedia, on the other hand, is a public encyclopedia that is free to be manipulated or altered as anyone see's fit regardless if their info is 100% accurate or not. Trust me, there is a lot of info that is inaccurate on Wiki. Especially when it comes to Star Wars lore. I recommend using only official LucasFilm material when shooting for the most accurate material available. Even 3rd party licensed tech manuals have some major mistakes. "The Essential Guide to..." series is a good example.

Vessel type: T-65 (X-wing) Starfighter
Designer/Manufacturer: Incom
Combat designation: Space Superiority Fighter
Crew: One pilot
                     One astromech droid
Power system: Nolvadex 04-Z cryogenic power cells and
                                     Ionazation reactor
Propulsion system: Four Incom 4j.4 fusial thrust engines (rated at 300KTU)
Flight control system: Torplex Rq8.Y flight control avionics package
Maneuverability rating: 75 DPF
Navigation: One astromech droid (usually a R2 unit)
                                           (carried in a patch-in cradle behind the cockpit)
Hyperdrive: Incom GBk-585 motivator drive unit
Sensor systems: Fabritech ANS-5d unit with
                                        LR Phased Tachyon Detection Array (PA-9r)
                                        SR Primary threat Analysis Grid (PG-7u)
Targeting computer: Fabritech Anq 3.6 tracking computer with
                                              IN-344-B "Sightline" holographic imaging system     
Weapons: Four Taim & Bak IX4 laser cannons
                                     (single fire or fire-linked)
                            Two Krupx MG7 proton torpedo launchers
                                      (three torpedoes each)
Defense: Forward/rear projecting Chempat shields
                                      (rated at 50SBD)
                        Titanium alloy hull (rated at 20 RU)

X-Wings, according to the X-W flight sims, have two tubes of three proton torpedos each.

They didn't take more than one attack run per group of Rebel fighters because the Death Star / Vader's TIEs shot up the ships as soon as they left the trench.  Why do you think the Rebels were using the trench in the first place?  Because there were too many cannons on the surface for a direct approach.

And if you're going by the X-Wing games, which are a great, stable resource for Rebel fighter loadouts:

X-Wing
4 laser cannons
6 proton torpedos in (3 per tube)

Y-Wing
2 laser cannons
2 ion cannons
8 proton torpedos (4 per tube)

A-Wing
2 laser cannons
12 concussion missiles (6 per tube)

B-Wing
3 laser cannons
3 ion cannons
I forget the warhead loadout but it had both proton torpedos and concussion missiles.

Thank you.

Had a look at the wiki, but could not find any thing about the amount of protons. http://img473.imageshack.us/img473/9176/pilotmh2.jpg

Look to the far right. Says 2 launchers with 3 per tub.