Personally, I'd still practice the jump kick with 4, mainly because b3, 4 and f4,4 are used as combo starters/links, and being able to link your TU after those combos is essential.
Letting the pad go back to neutral for a small instant has seemed to help. Also, if you notice the TU isn't coming out at all as opposed to late, make sure you're holding the controller as straight as you minds eye thinks you are. I've noticed that sometimes I will start holding my controller at a slight angle, and won't be hitting the pad clearly.
Go go muscle memory.