I am at the miniboss with Rush Coil. Unfortunately, I cannot one round him with simple shots :( I am 3 shots away from it so it won't work. I guess I should switch to Magma weapon since I have no choice. Quite sure your version is much faster.
Edit: here is my file:
http://tasvideos.org/userfiles/info/20584096173162757
It's merely 19 frames slower than yours :((( IF we would somehow manage a one round fight with the miniboss, my version would most definitely be faster. Also, you forgot a minor thing in your version, ladder zip just before the gate. Again, if we somehow would manage finding those three shots and make a one round fight against the miniboss, we then would have a definite version. One possible route is to switch to Magma Bazooka right before the miniboss.
Edit 2: I tried using all Magma Bazooka on the miniboss but it's really slow. Slower than Mega Buster. So your version is the fastest one Diggi.