Not sure how much difference in physics there is between the Sega CD version and the genesis version, but I noticed this trick was omitted from the previous genesis TAS as well so I figured it would still be worth mentioning:
You can jump straight up from ropes/chains by pressing jump while in mid-air right before Jim latches on to the chain. Not sure if this still works in the CD version, but it definitely does in the genesis version and I can even pull it off on a console so there should be at least 2-3 frames where it's possible to trigger the jump. This is probably related to the "jump after hook swinging" thing that was mentioned a couple of pages ago, in that Jim is considered being on ground for a few frames.
With this, you can save a handful of frames in Level 5 by jumping off the chain and through the platform above at
this part instead of going all the way to the left and then back.
Something else also omitted by /*- is jumping over the last wall to the boss in Intestinal Distress. Again, not sure if that is still possible in the Sega CD version, I don't have an emu at hand so can't test it.
If it is, it would be done by simply jumping to the left at the end of
this stretch, right after the fish.