Not sure if this was already tested elsewhere or these numbers are already known, but I spent some time testing fullhop AC dair -> Finishing Touch on Sheik (given that Sheik is definitely a relevant MU for nearly any Cloud player). I tried to fastfall the dair, although the timing for doing so in limit break while still getting the autocancel is very late.
In training with her set to level 3 and stop on the 3ds on FD, this combo registers as a true combo (2 hits) from 50% to 120% (pre-dair percents) and kills [I think it works a little earlier but I am working in multiples of 5]. I was barely able to get it to connect at 120% (once of several tries), so rage will lower the top percentage (with dair then launching too far). It seems Cloud must always full hop finishing touch. At 85 I could fullhop alone and get it to connect, but at 90 I had to double jump, although at 75 doing it with a double jump was still easy.
So 50-75, fullhop after dair, from 75-85 do fullhop or fullhop double jump, and from 85-120 do fullhop double jump to connect this (although there still needs to be testing with DI and also some work put into figuring out how DIable this is).
My next goal is to figure out who is immune due to height restrictions (can the AC dair hit Pikachu? Ducking Sheik? Ducking Pikachu? Ducking Kirby?).
Also, does anyone know how much weaker the back half of Finishing Touch is? While these might not be exact (I did this last night and am going from memory), the front half of finishing blow killed Sheik at 53%, but not 52% on FD, while the back half killed at 64% but not 63%. I'd assume this 10% gap is variable on a few factors (might be larger for DDD and smaller for Jigglypuff, and smaller on a Dreamland platform but larger on Battlefield'a base), but determining what that difference is seems like something that should occur sooner than later, unless people are just b-reversing Finishing Touch as required (I have not checked if the move can be b-reversed at all, since some moves can't be, but if you can, that would seem to make this a moot point except in teams).