Is balsa not a nightmare to turn with chisels though? It seems very britle. Ive been investigating making my own floats at work. My mate in the modelmaking department (i work in a uni) reckons that the best way to turn float bodies will be to make up jigs with sandpaper. That way I'll get a smooth finish + the same shape every time, quickly.
I use a lathe attachment to an electric drill. Use square section balsa not round, why..... Its easier to center on the lathe. I then use a modelling knife with a new blade to slice off the 4 corners. Do not use chisels but varying grades of sand paper to form the shape. To dot apply to much pressure as the balsa will break.
After the bodies formed and before painting apply a coat of Humbrol "Dope". This seals the balsa and raises the grain. Then with a very fine grade of sand paper for a final rub down. This ensures a good smooth base to start painting
I use round balsa, I've got jig which has a hole the same size as the balsa, the jig has a smaller hole drilled through the centre. To use I push the balsa into the jig and the feed in the wire stem through the small hole, gives you a perfectly aligned stem.
Another tip, to get a a good smooth base for the float, mix talc powder with dope, it will fill the grain, two coats are normally all thats required.