Sorry about the Super Short Charge, you don't actually press down + B, you just press B in the end to get the echoes. The way i did was start running from a certain position (X) pressing B in the needed frames to activate Samus's echoes to break the blocks and then i performed the blue ball and reached the door in a certain frame. I caltulated the time needed for that and compared to the current 100% run strategy. I calculated the time from the same position (X) to the door in the current run and it took around 45 frames less, iirc. Maybe i'm not using the right strategy to test it, though.
Edit: Managed to save 8+ frames over the current strategy for the 100% run in the PB pack room before entering the gauntlet. It can probably be better optimized.
smv
Edit 2: I have good and bad news. The good one is i found a small time saver (3 frames in-game time i think) and it adds a "new" trick to the run. The bad news is you have to use a Power Bomb for it to work, so it will add some lag frames. Also the PB Blast covers what Samus is doing, so you can't really see the "new" trick. XD Unless you press "9" on your keyboard and disable the Transparency Effect, so there's no Power Bomb Blast.
The smv i'm posting is actually 1 frame faster, but the reason i think it can save 3 frames is i couldn't make Samus complete her unmorphing animation in the frame she touches the ground. Instead she touches the ground and completly unmorph after 2 frames. Anyway, see the smv below.
smv
Edit 3: I had an idea that was supposed to be much faster than the smv i'm posting, though for some reason the X-Ray doesn't work for a turn around right after Unmorphing. I don't know if it would be anyfaster anyway.
smv