Hi Colyn:
I did using sail plan gap seals on bottom of ailerons and elevator and a rubber seal in the flap well to seal against leakage when the flaps are retracted. I did not do a controlled before and after experiment putting seals on right after paint. Overall the plane has lower drag area than a standard IV (1.85 square feet vs 2.12 sq feet) but improved slickness comes from several sources including better engine cooling, no intercoolers (aspirated), and gap seals as well as careful attention to wing profile.
So on balance, I dunno.....
F