The following was taken from the Tower Hobbies website, under Great Planes 40 size floats, PREASSEMBLED (ARF)

SPECS: Float Length: 40"
Model Weight Class: 5.0-9.5 lb (2270-4310g)
Model Size Class: .40-.60
Approximate Weight of Assembled Floats: 1900g

COMMENTS: The box says they are 34.5" long but they are really 40".

These floats are fiberglass, not wood. 1900 grams = approx. 4.2 pounds. Your LT-40 probably weighs 6 to 7 pounds. With those floats on it you're looking at over 10 pounds. You probably won't like the way it flies at 10+ pounds.

The Falcon Trading floats (33 1/4" long) weigh less than 2 pounds with struts, and a decent set of foam core floats would probably be even lighter.

Jim