Hey:
A good way to seal your hinge gap is to cut a strip of monokote about 1" wide (same color as the surface) and apply one edge to the fixed surface then down into the bevel, then (after removing the clevis) deflect the aileron or elevator the FULLEST amount possible and seal it against the beveled egde of the control surface.
I hope I have explained this clearly enough.
The hinge gap isn't a serious issue unless you fly fast of pulling form a steep dive. Excessive gap can cause FLUTTER. Flutter can and will cause serious control problems and I've even seen control surfaces leave an aircraft due to flutter.
You're doing the right thing by sealing these gaps.
If your fixed surface is a different color than the control surface, you can get clear monokote to seal these gaps!


Tom