The round shape with a fin style keel gets all it's stability from the rotary displacement of the CG of the keel. The center of bouyancy stays relatively fixed. Boats with a flatter hull shape shift the center of bouyancy to the leeward side and gain initial stability - but not ultimate stability. The inverted stability is also something to consider.
I've been told a local race boat (narrow and light) with a 10' bulb keel came back from Fall Off Sounding through the Sluiceway by Old Silas (a big rock). Seems to have gotten set a bit to the E by current into unsuitable waters. Left there with 7' draft and no bulb. Personally, I'm surprised the keel stub didn't tear out of the boat and sink her. Same source says she's currently hauled in Mystic - not blocked as high as usual.