skamastaG, I did some testing on YI4 and actually came pretty close to crossing the gap. I realized early on that I suck at doing it the traditional TAS way (pick up the shell, hit the star block, drop the shell, then kick it), so I came up with a new way to do it. Instead of picking up the shell and dropping it again, I just kick it right away, when I first get to it. Depending on the speed you kick it and where you jump, 3 different things can happen. These three things are all shown here, played "non-tool" (except for the savestates).
Yoshis Island 4 Tricks
Option 1: This is the very first thing you see me do in the video. For this, you kick the shell slowly and jump into the star block. When you come down, you will bounce off the shell as it is over the pipe. This really has no chance of making it, but is pretty entertaining if you cant get anything else to work.
--The second thing I do in the video is a rare mess up of this, I usually get it every time when I try.
Option 2: The third thing you see me do in the video. You kick the shell so slowly that Mario runs into it, but doesnt kill him because he's big. Ideally you jump as close as you can to the star block without hitting it, and like Fabian said, keep your jump short. This is really just an easier (and worse) way to do option 3. Comes pretty close to making it.
--The fourth thing I do is a semi-rare mess up of option 2.
Option 3: The fifth thing I do, this is really the best option. It's pretty much the exact same as option 2, but Mario doesnt get hit by the shell. This comes really close to making the gap, but is harder to do than option 2. Its not actually too hard to do though, I can get it probably 1 out of 3 tries.
Can anyone verify if it is indeed possible to make the gap using option 2 or 3? This would make it much easier than the current TAS way.
BEST TAS EVER!