You were just asking about the up air to grounded up b.Sounds like it could look really cool. I'll try this out on some opponents.
In your lower percents example, in that same situation you could also end it with a jump to falcon punch, right? Though perhaps the upb covers more DI options.
Up air to Falcon punch works without having to do that. The Falcon punch is also too slow compared to the up b there
It is possible to up air to falcon punch as long as you touch the ground right after the up air
I believe it works at 60 percent (as in 60 when you up air). It probably works until 70 or so.
Though if I am going for a Falcon punch ending, I try to combo into a grab to falcon punch as it is much easier to time.