I guess that if the keel won't take that weight, you have a keel that's likely to fall off! I've seen that happen once. Following a fairly shabby sailing boat into Yarmouth (Isle of Wight, near Cowes), and suddenly it rolled over. Strangely, the underside (now the top-side) was smooth!
It stopped straight away as the mast stuck in the mud. Nobody was injured, but they did look surprised. We picked them out of the water and anything we could see floating, but goodness knows what went to the bottom.
Strangest Mayday Relay I've ever sent.
