The TAS looks great so far! By the way, I just realized that you may not have been taking the fastest route in the basement in your test run. When you make your way from the key door to LLL, instead of going straight, right, door, right, left, straight. Try going left and long-jumping up that slick incline (with the blue glass above it), go through that door, quick left, door, straight/right and then LLL. Just a quick couple runs with my stop watch showed the second way to be faster, I'll investigate further though.
Further testing shows the following results (not perfected, pretty good):
My way: 11.3 seconds
Normal: 10.4 seconds
It may be worth taking a look at though, I didn't really perfect the alternate way and it's a little tricky.
Here is a movie of the alternate way, it has a couple little tricks in it:
http://www.people.virginia.edu/~avw6s/random/Mario64_AlternateBasement.zip
Here is a faster version (doesn't have turn trick, not sure if the trick is faster, comments welcome)
http://www.people.virginia.edu/~avw6s/random/AlternateBasement4.wmv