OK guys, I made a test TAS of the new GBT route. I got it down to 34 explosives for the boss key skip, plus 4 for hovering over the gap in the control room, for a total of 38. I'll upload a video soon, and I'll try to get frame comparisons to Mukki's run done quickly. Initial estimates tell me that we may be looking at a time saving of 2 minutes here.
Oh, and it turns out that, with that one bombchu saving method where you switch to the Zora Mask, you can break the lock by targetting a bombchu that you dropped to do a hover with. The timing is very precise, though, so it's probably not good for unassisted.
EDIT: here's the frame data
Main dungeon. Timing begins after entering the control room and ends upon the fadeout while entering the boss room.
Mukki - 14570 frames (4:03)
New - 8057 frames (2:14)
Difference - 6513 frames (1:49)
Also, I think I improved on his boss fight.
Mukki - 2043 frames (:34)
New - 1566 frames (:26)
Difference - 477 frames (:08)
I think we could go sub-2:00 with the run.
EDIT2:
http://www.youtube.com/watch?v=E2PyzRDoSxk