46Marcus: I flew a SrTele for years on floats. I Used floats extremely similar to those from PlaneFunFloats.
The ones from Seaplane Supply are also good.
I used floats that were 45" long. My tele weighed 10 pounds with floats and an empty tank. OS.91 four-stroke.

Both the sources mentioned supply floats with a solid styrofoam core. Very light, very strong, very efficient, and they CAN'T leak.

Other post mentioned several suppliers of floats and all those were hollow, plywood floats. They tend to be at least twice as heavy and when they leak (not IF!) they can hold a lot of water. If the water sloshes around your CG will change with it. If only a teaspoon or 2, then it'll be just enough water to feed a science project inside the floats. (Ick!)