ORIGINAL: KWJ48
I did notice (with my set-up) on tight loops it liked to snap out at the top.
This is quite common with the Ultimates... There is a range of elevator throw where this will happen.
Either INCREASE or DECREASE the throw until it stops.
Increasing causes both wings to stall equally stopping the out of round... decreasing lessens the stall with the same effect.
I increase mine to the point that the high rates stop going out of round on the tight loops and the low rates give me big unstalled loops.