I was just looking at the bird boost in 5-1 (24309) and it looks like an extra blank frame in that jump lines up the coming de-spawn so 3 back-presses work instead of 5, but that makes the bird much harder (impossible?) to avoid later. Is this something you've already ruled out?
Also:
Is it possible to use the RTA trick and still boost off the bird later?
Wow, I didn't checked that earlier, but it's actually 7 frames faster to do that (because this way the bird is farther on the right side). To be sure, you meant this: blank frame before next despawn and only 3 back press, at least that's what I did now.
Yes, and it was 5 frames faster but the 5-2 final knife bitch was bad. If we are lucky with both improvements (5+7 frames), maybe this way the knife bitch can be avoided, gonna test it tomorrow.
Btw, thanks for your "continous" input regarding ideas, because most of the time you are right :D
edit: using the RTA trick and boosting off the bird, the 7 frame improvment can't be done because it requires 4 back presses to despawn the pillar guy. I uploaded my route with the RTA trick that desyncs at 5-2 knife bitch.