One thing I've noticed
...lying on my back under the wings grinding away at the inboard edge of the flaps to let them bypass the fuselage sides and assume three degrees of reflex against the rear spar, is that a lot of the rubbing noises I feel and hear during this process come from the flap hinges themselves, not the interference of the flap with the fuselage. The contact of flap with fuselage pushes outward on the flap spanwise, and causes the hinges to flex enough that they rub like scissor blades past each other near the upper limits of travel. That kind of flex means that spacers will not solve your problem enough to protect the paint. More important would seem to be making sure there's enough relief between flap and fuselage that retraction does not shove the flaps outboard and cause the hinge arms to shear past each other.
I've only started this flap fitting process last night, but that's my take-away so far. The fitment effort has required complete sacrifice of the fiberglass closeout of the inboard flap rib that I so foolishly did last spring - that piece doesn't see slipstream in cruise so there is no drag reduction benefit to be had from plugging it flush. I failed to think that through beforehand.
Hop-Along Aerodrome (12VA)
RV-6A - N30YD - flying since '98
RV-10 - N130YD reserved - under construction
donating monthly to the VAF - thanks, Doug