what are the rules for it?
person has to be in a corner? and is it a buffer or just a link, ive been having trouble linking it
They have to be crouching.
Opponent has to be crouching in order for it to work. I dont think its considered a link either because the super has to be done after the overhead frames are done. Its good on wake up but dont abuse it. Easily parried.
its also good after a cross-up j.foward for a mixup. Timing just takes a little practice. Good Luck:wonder:
I think you might be confusing links with cancels. Links are combos where the second move has to be executed after the first move recovers completely. This differers from a cancel where you cancel the recovery frames. Back and MK happens to be a link.
Other examples of links:
Far standing strong into SAIII with Ken
Akuma can link SAI off of his close forward (the knee).
I hope that clears things up a bit.
There you go. I was talkin outta my ass again x_x
1hitparry with the assist:lovin:
thx brotha
EDIT: now that I think about it I think i meant to write cancel anyway haha. None the less, good save 
Yeah, I posted on a Makoto thread that low strong combos into short, which is complete BS. Sometimes I say things without even thinking.