Sorry for the lack of updates in the last days, but I've spent some time overworking my run (and still haven't finished it).
First of all I did some small changes in Yoshi's Island 1 and Yellow Switch Palace, just "optical tuning" which didn't affect the time. In Yoshi's Island 3 I followed Mazzic's proposal, and yes it did speed things up a bit, but unfortunately not enough to finish the goal 1 frame faster (just 1 pixel earlier, hooray :P).
Then I did Donut Plains 1a again, as I had found out that my old time was not yet the optimum, so I could improve it by 7 frames and also bumped on one more super koopa, resulting in one more 1UP :)
Unfortunately this somehow affected the fade-out time in Green Switch Palace, which then forced me to hex in some small delays before entering the levels to avoid desynching, so by the time I had reached Castle#2 I had already lost those 7 frames again... :S
Then, when looking at the video for the 100th or 200th time, I suddenly had an idea. There must be a way to improve castle #2, and get rid of that stupid long wait before entering the red door. I had already tried out flying all the way up with spin-jump flight, because this maintains running speed and therefore it should be possible to just lift off again after landing. But somehow I never could reach enough height when lifting off a 2nd time. But this had worked well in Gnarly, where I also needed to rise up very high. So, after some more testing, I found out that I needed to run for a short time before lifting off again, and then Mario would rise high again. So now I could reach the trampoline not only a bit faster, but also with running speed, so I didn't have to jump on it, but could just grab it and fly up with the trampoline. Blasting through the blocks caused the loss of running speed, and I was then forced to wait a few seconds because a stone blocked the way, but with the help of the trampoline I could now enter the red door 309 frames (= 5 seconds, 8 time units) faster!
So far, so good. I hexed the fight against Morton into the new video, and it worked perfectly fine. The fade-out sequence took a bit longer, because I had saved 8 time units more. And then in Vanilla Dome 1, the video desynched. And unfortunately, a delayed level-enter also didn't fix this, I tried out like 7 or 8 different frames. I *think* it has to do with the fireflower->feather switch, so now I did this in the fade-out sequence after Morton's fight. And I'll have to do Vanilla Dome 1 again, at least the first room... And wish me good luck that the other levels do NOT desynch so drastically :S
Anyway,
here's the new video up to Vanilla Dome 1, I'll add the rest of the levels tomorrow.
@Volkov: I'll try to make a little hex tutorial in the next days. I use
A.X.E. as a hex editor and am pretty happy with it (I have version 2.0 though, it was freeware back then :D)