My recommendation is to maintain good form, and allow your body to adjust first before worrying about moving into the fully suspended movement.
I myself just recently started being able to complete the incline presses fully suspended. I started off leg down until I could get that shoulder strength. Another thing I found that helped me maintain stability, is lengthen the TRX 8" - 12" from the ground like doing suspended lunges, hamstring curls, etc.. as opposed to fully lengthened. At full length, my body would sway from one side to the other.
I tend to superset suspended lunges and incline presses. So I'll do x amount of reps of suspended lunges on say the right leg, then flip around and walk back a couple steps and do the same amount of incline presses, then switch legs and repeat.
Hope this helps. 
Thanks,
Justin