Cubmaster126, If you find your plane (with floats added) is less stable than before, you might consider adding a sub-rudder just as with full-scale planes.
You might want to see my discussion on
http://www.rcgroups.com/forums/showthread.php?t=249773&page=2 , (See Post # 19). Also try a Google search on
airplane subrudders.
Virg.