I've been doing some work with this game lately and have found a couple more tricks using rush coil, some more useful than others. I'm going to dump some of my finds here as soon as I sort out whats what here.
Edit #1
Jumping into a room transition from below the screen:
http://tasvideos.org/userfiles/info/8484842132492839
Situationally dependent trick I found that allows you to jump up from underneath the room transition. The only place I've found it to almost be useful was in the second room of Napalm Man's stage, and I say almost useful because compared to the test run I did without using this trick, I found it was 28 frames slower. I was recording at 12% for both tests, so it's possible that it's because there's still reaction time to account for, even if it's at ~8 FPS.
Edit #2
Low speed test run of the game:
http://tasvideos.org/userfiles/info/8485062119959801
Recorded at 12% speed, just like the Napalm Man demo above, following the route of Star Man, Bright Man, Napalm Man, Stone Man. The route was decided after doing a handful of level test runs with Star Man's stage being the fastest for me to complete. I had made this prior to finding the trick above, but after I found the ability to zip and clip using Rush Coil. Nothing too spectacular until Stone Man's stage in my opinion, but that's just because it contains all off the zipping and clipping in the run. Also found in Stone Man's stage towards the end of it is a bizarre trick I found while recording it, and only seems to work there too, which allows Mega Man to wrap around the screen bottom to top. It may be faster than just going through that section normally since it allows you to forgo grabbing onto the ladder and hopping up some 1 block tall ledges in favor of sliding across the ceiling, but it was not tested.
Edit #3
WIP:
http://tasvideos.org/userfiles/info/8485472536304864
After spending the better portion of a cumulative ~12 hour car trip working on the above test run, I decided to attempt TASing it myself. I'm following the route that I used for my test run. My current progress is part way through Bright Man's stage, feedback would be appreciated.
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Mine : 
Not even sure where I gained the 4 frames. I think it was optimizing sliding? I'll upload the file after I finish the stage.
Observations:
*Sliding can be cancelled by pressing the opposite direction for one frame, which allows for much earlier jumping when necessary.
*Jumping off ledges is faster only when a single frame jump is required, otherwise it's faster to just slide off.
*The fully charged shot seems to create a bit of lag whenever it's fired. Cancelling slides and using single buster shots might end up being faster in rare cases.
