Iin reply to the problem of aileron ineffectiveness it could be that the pendulum effect of the floats is counteracting the ailerons. I'm not saying that the ailerons are ineffective it's just that the deflection of the downgoing aileron is creating so much drag that the weight of the floats is not allowing it to roll.
Two, or possibly a combination of solutions are possible. One, adjust the ailerons so that you get about three times as much up aileron as you do down, and two, couple your ailerons and rudder together. Down aileron drag is a reason that full size sailplanes always seem to use rudder and aileron together. It is particularily noticeable in slow flying airplanes.
I think you will find differential ailerons will solve most of your problems,
LOL, Peter