Ed, trim your plane for level flight, then fly inverted. That's when you'll notice the weight difference. Your plane will cork-screw through loops etc.

For all you guys who are wondering... Finish your plane. Have it ready to fly. THEN balance it, both CG and laterally. shift your batteries or add weight to the nose or tail. Then add wingtip weight if needed (and I've never seen a plane that didn't need some). I usually use split-shots, then once you find the right amount, remove 1 or 2 (depending on their size) to allow for the weight of the epoxy you will be gluing them in with. Now drill or cut a small hole in the bottom of the wingtip and drop in the epoxy-coated weights. Re-check the balance to make sure you got it right. Then apply a small patch of covering over the hole.

( I know it's a heart breaker to put a hole in your new airplane, but there's no sense in doing it before the plane is ready, and no one will ever see the little patch on the under side.)