I had a TT46pro on my Ultra Stick and if I remember correctly an 11x5 prop seemed to be the sweet spot for me.
While the plane flew well enough, it really didn't have much vertical ability, and I do understand your desire for it to be able to fly straight up for at least a little while.
Wifey bought me an OS 70 for b-day or Christmas (can't remember which) and it really brought the plane to life.
Someone else already mentioned switching fuel, I used to run 10% fuel, got a good deal on a case of 15%, I didn't expect any noticable performance differences, boy was I ever surprised.
Switching fuel is well worth trying to see if the extra nitro will get you where you want to be.