Whirley Bird,
I think the 46 LA did not have enough power with the extra drag of the floats. Nose weight may have helped but I was discouraged after my initial tests and bought a Ace Seamaster. It is a great flying sea plane.

Alstack,
This is how I set up my rudder. I just used a Y-cable and an extension and plugged it into the rudder channel. I had great water handling with it. Let me know how your setup works.
This is the rudder I used http://www2.towerhobbies.com/cgi-bin...?&I=LXE981&P=7