To be honest...I forgot to link this to you when I was finished with it, but it was 11:00 PM and I was tired. Better get used to this (its the college norm for me. XD).
Anyways, this is a preliminary list of the percentages that work, the ability to counter-attack, etc., for sourspot U-Tilt to D-Air, based on an opponent that does not DI (I have explained this a lot) and without staleness (staleness allows us to combo at bigger %s), otherwise known as Training mode. Again, it is a preliminary list, and I'd be more than happy to constantly update it for better accuracy. This is what I found, in a chart form. Hope you guys enjoy!