Right now I'm testing just trying an odds and evens approach: 13579B, 2468AC. This will fill the queue as quickly as possible, and guarantee a bomb will get crumbled within 12 attempts if there is one on screen, and keep my sanity by not fiddling around with random garbage.
The game's crashing very frequently, possibly always, if I input end with the queue at 240+ full. So there may be a decent upper limit here. Still playing around with it.
There is one issue though, Pad 11 and 12's inputs get used at that very moment to the LIFO if there isn't currently a bomb being crumbled, so the queue ends up with none of them in that case. Right now, I patched that by just starting a new bomb crumble before I start my spam, as well as having a bomb ready to crumble on B/C during the spam, so I'd have some Bs and Cs deeper in the queue still. Less, but enough to survive.
I did get good Sign Guy luck and a successful input end 89 frames faster (9709). Queue started at 235, ended at 33 left. Will keep playing around for the next few hours.
edit: 9678, 244 start, 57 end
9636, 238, 46
9567, 239, 24
9538, 240, 5
9532, 245, 7
9525, 244, 9
9522, 249, 9
9513, 240, 30 (wow, lucky)
9512, 242, 14
9509, 245, 22
9501, 245, 7 (this one took a while)
9500, 243, 0 (I wanted a round number)
9499, 242, 3 (but then I remembered the movie length is actually one frame after input end so I forced one more out)
There could be a bit more frames squeezed out still probably, but the RNG is getting very tight, plus this RNG has an egg spawn after the last bomb, so, entertainment B)
http://tasvideos.org/userfiles/info/63849490957770407