So, here is a wierd situation; check out the S2 9.1 on yachtworld (YW# 22624-1744489) Turns out the driving reason it is approx $10k under normal asking price is that they have turned a fin keel into a shoal draft by cutting of about a foot and adding a bulb. It is reported to be a very clean job and looks ok in the pictures. My initial reaction (and 2nd, 3rd, etc.) is to run away butt.....
This is not that unusual. In an earlier post I mentioned Mars Metals, which is a company that does this. They are known locally for the "Mars Bulb", which is a hydrodynamically designed torpedo type of bulb put on the bottom of fin keels. The weight, placement and shape of the bulb are carefully calculated based on the shape of the hull and keel.
It is my understanding that they started doing this in order to compensate for weight lost when some die-hard racers decided to modify the shape of their fins, shortening the chord in an attempt to emulate boats such as the Mumm and Mount Gay.
It has also been done for some people who have grown tired of running aground in shallow waters. I don't think you should discount the boat because of this, it would be worth researching who did it, and how much time and thought was put into it.
I would not discount this boat based on the keel alone. It looks like a professional casting...