ORIGINAL: RCKen
Sealing the gaps won't give you any more throw, but they will definately improve performance. It's not really hard to cut and rehinge the surface, it just takes a little bit of time. If you don't have enough throw then you might want to remove surface and reshape it so you have more throw.
Hope this helps.
Thanks, Ken and everyone.
I'm sure the re-hinging is do-able, just sounds like a royal pain, since the wing is covered and I'd prefer not to de-cover it. So if it comes down to it, I'll use hinge points and not c/a hinges.
Of course, this is a trainer, so I don't need a huge amount of control surface performance. Not like it will be doing a lot of axial rolls.