Just installed the GP floats on my 80" H9 J3 Cub and I'm trying to get the CG correct but its difficult since the floats cause a pendulum effect and makes it hard to balance. The plane hangs slightly tail down - I think - how should the plane hang when checking balance with floats? I took the airplane out for the first flight test and it seemed really elevator twitchy (tail heavy) and also wanted to roll right so I added down trim and left roll to compensate.
Should I add weight to the front of the floats? If so, are there any weights that are pleasing to the eye to use? Also, I'm using a Saito 72 and it goes through the supplied fuel tank in about 7-8 min. Is there a larger tank I can fit into this bad boy?

This is what I'll try:
1) Move battery forward under fuel tank
2) Try to get larger fuel tank
3) Add weights to floats?
4) Adjust ailerons for roll problem?
5) Add up trim on both ailerons?

Any help would be great to get this plane flying safely!!

Thanks!