I just saw your WIP and I want to say it's very entertaining! I like how red and blue just can't stop throwing each other. My only other suggestion for entertainment is maybe some leapfrogging, it would have been especially nice to see some during the auto-scrolling slope section.
However, there is one very big flaw in your run. You forgot to skip boss text. Hold B the moment the boss text appears (not before like you did), and you'll scroll through the boss text much faster. I know it will be annoying to redo part of your run, but I don't want you to miss out on something so simple (like Jackic did in his run).
During the mine cart stage would be a great time to chase red around with the flame chaser. You will have a ton of free time, and you can do the mid-air levitation trick to loop around the flame.
BTW, maybe you'll get some tips from my speed run. I know it's old (almost 2 years now), but maybe you will discover something new. And it's a good excuse to whore myself :P
http://speeddemosarchive.com/GunstarHeroes.html