Kriller37 | SMB2J Fast 1-2 Clip Set Up @kriller3771 | Uploaded 4 years ago | Updated 8 hours ago
EDIT: Apparently Lekukie found this set up a little while ago and I didn’t know about it, and happened to also find the same set up on my own. So shout outs to lekukie.

Tecate's recently found set up ( youtu.be/gdiMuRq-LoY ) gave me some ideas on some set up ideas, and I ended up finding this one.

The set up:
R+B at the start, then full jump off of the right side of the middle ? block, which is frame 129. Then release B in mid air, and repress B the frame you land. You can do sockfolder inputs when you land, which is shown here, but the jump right after the B press isn't required. As long as you jump at least 1 frame after pressing B, you'll be set up with F7, which is optimal.

If you jump 1 frame late, and still press B the frame you land, you get D5 alternating, and are still set up to clip in. (D5 is the same positioning you have for smb1 4-2 blazit clip, so this is still very doable to clip with).
if you jump 2 frames late, and still press B the frame you land, you get B3 alternating, which requires a pretty well timed left press to clip in the wall (2-3 frame window, depending on subspeed), but is still super doable to clip with.
Jumping 3 frames late and still pressing B the frame you land gives 19 alternating, which is still possible to clip with, but much harder. Requires a frame perfect left press to clip in.

Haven't looked into back ups for pressing B a frame late yet, but I'm sure some could be found. Also its worth noting that jumping a frame early makes you short the pipe and fall in the pit, so shooting for jumping on frame 129 or 130 would probably be best.