I scratch-built floats for the LT-40 I learned to fly on. They are based on the "40-size" float design from Great Planes, but I scaled them up a bit because the GP floats sit too deep in the water. Balsa and a bit of ply construction, covered with 1.5 oz fiberglass on the bottoms and 0.75 oz on the sides and tops, sprayed with silver aluminum engine paint. Ernst water rudders driven from the stock nosewheel system on the plane.