People who have trouble flying floatplanes with the same power that works for them with wheels have bad float setups. Floats are more streamlined than wheels, and even though they have more frontal area it does not mean they make all that much more drag.

THe step of the float should be under the 40% point of the wing chord, or just behind the balance point. THe floats should be mounted so that with the tops of the floats level, the wings have some positive incidence...3 or 4 degrees at least. Floats should be mounted rigidly....flexible landing gear is for grass runways.

The floats should be at least 75% as long as the length from the propeller drive washer to the rudder hinge. And that should be long enoug so that the floats stick out in fron of the prop by 1/3 of the prop diameter. If your plane's size is such that the 75% rule is halfway between 2 sizes of floats, go for the larger size.

Water Rudders should stick down no farther than 1/2" lower than the transom of the float. You do NOT want the drag of the water rudder while you are trying to take off. Water rudders are only for taxiing, and they should not touch the water after the plane is "on-step"

Plywood floats tend to be heavy. Fiberglass floats tend to cost a lot. Blow-molded plastic floats tend to make high-speed boats out of airplanes. All the above are hollow, and make a good place to store water which, at 62.4 pounds per cubic foot, is contrary to getting airborne. Especially when they are partially filled and a big slug of water sloshes to the rear of the float, carrying the center of gravity aft with it. This makes for a particularly short but spectacular flight, followed by a boat ride to retrieve the pieces.
Foam floats are leakproof, efficient, light, and durable.