I've owned and sailed a C22 and I have to agree, down flooding is the major peril. I forgot about the keel lock bolt. On many C22s they don't work anymore because they've been bent by the owner raising the keel with the botl tight. I had to grind out mine and replace it.
This thread also made me realize I missed the whole hazard of a knockdown with my own boat. However, while it would scare the hell of me, the outcome would surely be different. It's an ETAP, with a foam filled double hull. So even with down flooding it won't be sinking. Also every hatch, even the companionway and slide is fully gasketed. So if I'm closed up, as I do if the weather is looking bad, I probably won't need more than the sponge. There isn't any bilge pump, so that is good!
I've often suggested to sail boat owners to sit in the companion way and imagine in your mind what would happen if your boat was very slowly rolled over completely. Picture what the interior will look like when she is completely upside down. Cushions on the ceiling? Floorboards on top of the cushions? Smashed batteries spilling acid? All of your galley, food, clothing etc. added to the pile? Now picture it all happening in a split second! Are we all prepared?
Gary H. Lucas