The plan is a short (3") double ball as the one you describe, and the final long (5") ending with the strobe. Simple, but hopefully flexible enough. With a flat front compact and one strobe only, I hardly attempt any wide angle, so hopefully this gear will give me the flexibility to do macro and a few middle angle. Am I missing any key piece? I had to learn on the spot what's needed in this kind of systems...
Nope, definitely no flotation needed. The case is strongly positive, and even with the strobe I use some 300 g of extra weight attached to the present tray. Will need to reconfigure with the new system...