Just to add to what Scott said..............
Once you get the flaperon surfaces flat, and need to "tweak" the flaperons for roll trim, do so with VERY small adjustments. It is easy to overdo it. Ask me how I know
It will most likely take several test hops with very small squeezes each time.
Another suggestion. Pad your seaming pliers with foam (sticky back weather stripping works good) and use them for the gentle squeezing. The 3" surface will help you not to kink any spots in the metal.
John Peck, CFII, A&P, EAA Tech Counselor, Flight Advisor.
Master Pilot Award, UFO Member.
RV-12 N37JP 120176, built 2011, sold 2020.
One Week Wonder Build Team, OSH 2018.