I put the flaperon root flow fences on my APIS as well. I also have mylar
gap seal on the lower surface only, plus some interior "V" seal along the
top and bottom of the flaperons.

I've never flown the plane without the flow fences. If the seal strip
(fuzzy piece of velcro) is narrow and the flow fence is waxed, then these
add very little to the control forces. However, when I added the gap seals,
I did notice an increase in force at the stick to move the flaperons. While
this is noticeable on the ground, I've never really been aware of it in
flight.

FWIW.

John Scott