i don't know .I'm assuming you flew it already to know that it's too much. just dail it out accordingly.
It's hard to say what's too much for you. 50% sounds like a good start , if it's still too much, dial it out.
if it's not enough dial it in. if you havn't, finish your club and make the transition from your trainer
to the cub first instead of going directly to a warbird.

The cub is not a flat bottom with less diehidral so it'll roll more than a trainer but not as much as a hot rod.

or just not it a hole in or out via the cleves or control horn..

Keep the linkage closest to the servo's center to retain torque. moving it out will give you more throw
but you'll loose torque.

you do seal your hinge line don't you ? via clear tape or mono coat . this will prevent air leakage to the control surface.

like opjose said..that's one of thing i hate about trainers, it dosen't roll fast enough when you get in trouble.

So its just a matter of you putting flight hours in