It could work.

Or, just stick a rudder down from the nosegear and use regular floats. If you elect to use a small float, make sure it has a keel/skeg so it WILL actuall cause steering instead of just sliding sideways. AND make sure it can't tilt so it could hit your prop or be pointing in the "DIVE! "direction when you land. Also, check the steering and adjust it so it won't strike the other floats when turned.

For all the advantages a water rudder gives, all its disadvantages are caused because it is at the rear of the float.

Stick a water rudder at the nosewheel position, and make sure it sticks down no farther than the bottom of the float where it is installed. Set the plane on a board, and make sure the rudder does not keep both floats from touching. It will still steer, and it will be out of the water when you take off and land. AND, it won't make your plane weathervane toward the downwind direction like some water-rudder installations do.

It might cause some spray in the prop when you taxi slowly, but that's not a big deal and that is the only time it should be in the water.