Don't forget the pyro red leader!
One of the things that I never see discussed is the timeline of the shooting, the disappointing (to George Lucas) first generation of pyro detonations, and the 2nd generation of shots filmed by Joe Viskocil.
I've read in several vintage publications interviews with Joe, and he mentions that there was a lot of pyro work done before he came on board, and that GL was not satisfied with this work. The first set of explosions were said to be flash-bang, whereas George wanted the flaming fireball look that we are now familiar with in the movie.
A quote from Cinefex #65 puts it fairly succintly : "After a series of primacord mishaps - resulting in the obliteration of dozens of breakaway models - pyrotechnician Joesph Viskocil was brought in to orchestrate the miniature explosions."
Now, if we watch the original Star Wars with an eye on explosions, we'll note that with the exception of Red 4, the X wing pyros are crude models with simple sticks for the guns, etc. It is also worth noting that there is that well-known picture of Joe Johnston and Joe Viskocil rigging a Red 4 Pyro. (Though it looks like a cruder version, as M. Tox mentions).
My theory: Richard Edlund et al blew up the beautiful pyros that we are discussing before Viskocil came on board. Viskocil arrived and then had to have the guys rapidly slap together some crude bucks for the remaining X wing work. As time was running out, the "pyros" became cruder and cruder. I think of the beauties in the pictures on the bench as "hero pyros", and ironically they aren't even in the movie for the most part.
Worth noting, however, is that the Red 4 "hero pyro" does appear in the original cut of Ep IV. It's the first X wing shot down, and is in a couple of quick cuts in flight before detonation as well. I posted caps in another thread some time ago.
Other sources corroborating my timeline theory: Cinefantastique Vol 6, No 4 from 1978, Starlog Photo Guidebook - Special Effects #3 from 1980.
Cheers.