I feel a lot more confident with that blimp shaped float spinning around on the top of my mast and I use it whenever I am not racing. The problems are: It is probably harder to right the cat with the extra weight. It is expensive and probably reduces your performance. If your mast is sealed properly perhaps you could get away with one of those foam wrap floats. I imagine they are lighter and offer less wind resistance, and they are cheaper.
The spinning bob I have requires riveting a rod to the comptip. I would like to hear from someone who has installed a foam float to know what they are like.
Greg
H14,H16