Bidule - that gap isn't horrible, but it's not great either. You should seal it to make the surface more efficient and also to help prevent flutter.

Whatever you do, make sure that the linkage can't flex at all.

Check out this page. The flaperon hinges are actually Oracover, but it would look the same if there were "real" hinges underneath.

http://www.airfieldmodels.com/great_gonzo.htm

To seal the hinge, remove the linkage, move the control surface to a full up position and then iron a piece of 1" wide or so monokote (or other film) to the wing and the aileron. Takes all of 15 minutes for both surfaces.