Gap sealing
It's a great idea, unless your model is a scale project, and seals would make it look "wrong".
On sport/aerobatic planes I've built, flown without, then with seals, the difference was obvious from the first flight. I seal the surfaces on all my planes now. I wouldn't worry about reducing the throws until you fly it and see the difference.
You could:
1. Seal the gap with a bit of clear tape on the underside of the surfaces, or
2. Use Monokote, during the covering process, to seal the gaps, or
3. Run a thin bead of silicone into the gap
I've used all the above methods (more info on my web site) and they all work. I think you'll like the improved response, especially noticeable in roll rates.
Happy flying!