I decided to take a look at this again after a bit of creative inspiration this past week, and I was able to shave off 294 frames from the last movie!
http://tasvideos.org/userfiles/info/36009974368461154
I cut 9 frames from BLW2 due to a better helmet collection, and the majority from just barely being able to pull off the bounce from the second to last tank to the top of the incline (made possible with better air drag reduction). More importantly, this saves an extra HP for Plethora.
The rest came from a massive overhaul on the Plethora fight. Due to the extra HP, getting Micromax is no longer necessary, saving 112 frames from transformation time alone. I then experimented on several different methods with Red Stealth, the best outcome actually being far away from the flag, due to the arrangement of obstacles between that area and the flag. In the previous movie, I had to jump off a platform to the flag 75 frames after Plethora was defeated, but now the last input is made 70 frames BEFORE Plethora is defeated. Additionally, I found a funny side-effect of running off moving platforms while ducking every other frame, which teleports me instantly above Plethora, saving some frames (if you don't know why it happens or why it's useful, I could explain it if you'd like).
I'm aware that the title of the bk2 says the time is 1:21.95, but when using the actual console framerate, it's actually 1:22.07. If I can get the latter time below 1:22 (-5 frames), I'd be satisfied with the outcome. But right now I'm at the point where new frames to save are really hard to come by, and I was wondering if you can offer any insight as to where further saves are possible - if you have the time of course.
My .tasproj file still has branches of other Plethora methods I did that didn't end up being faster. If you want to experiment with those as well, I can link that file here too.