The best thing about the UM T-28 is that it slows down really nicely. It is so streamlined that if you're moving fast and back off on the throttle it seems to just maintain its fast airspeed, so climb to scrub off some speed, then proceed at a slower speed. At that speed it has a lot more in common with your Champ and you'll be able to adapt.
Pop her up to treetop height, slow her down and start to enjoy. Keep your control movements tiny and fly by "thought control." You have to turn that corner from anxiety to relaxation before your brain will turn up its learning ability.