The Van's 'Wing Incidence Angle Made Easy" guide suggest test fitting the flaps... stating "It was the hope of the designer that the flaps fit on the wing..." It is certainly my hope as well.
The flap must be trimmed to fit nicely against the fuse, it is a compound curve, fortunately Vans supplies a template on a drawing that is aligned along the inboard rivet line. Traced the template along the right flap, then trimmed the flap just inboard of the trim line using snips. Smoothed the edge with a file on the flats, scotch brite pad on the curve.
To test the flap on the wing, had to reverse the clamp holding the wing in alignment (of course without losing the finely tuned and time consuming obtained sweep, incidence angle and VS distance in the process.)
Installed right flap and determined just a bit of additional trimming needed to allow the flap to go all the way to the 0-degree position. The flap bottom skin where it is common with the fuse is supposed to just 'touch' the skin. You can make some adjustments if needed, and there is no harm aerodynamically if it has to be trimmed altogether. I think in my case I'll be able to have the skin just touch.