I was planning on doing the sink test on my new BAM in my pool once I open it. Was thinking I'd use a 701 and block off the intake. Even if water gets in through the pipe, it won't hurt a fogged engine all that much. I'd have it cleared out and running again within a few minutes.
I'd like to find a small air bladder I can put in the nose. I think that would be much more effective than pool noodles, but for now I have the noodles jammed in there. I also have a small buoyant orange rope under my pole, held on with an elastic. It's similar to paracord but a slightly lighter. If the noodles buy me 30 seconds before the ski sinks, I can rip the rope away and it'll be long enough to reach the surface anywhere in my lake. I doubt it would be strong enough to pull the ski up, but I would at least be able to locate it. Where I usually ride is only 15-20 feet, so I'd get the boat, dive down, tie a strong rope to the ski and pull it out.
I guess running a larger fuel tank, half full is somewhat of a safety measure. That could easily add 10kg of buoyancy.