Perhaps what is needed here is for a builder such as Winder to offer a single bottom option. They have developed a very stiff Merlin along this theme so I would think a 12 could be easily adapted. The problem of going it alone is one of investment and the risk you run of spending a lot of money on a boat that maybe you would find hard to sell, if it has the backing and name of a builder like Winder then you mitigate this I think. I know of some crews (mine included) who refuse to sail a double bottomed boat a problem that probably was not considerd at the time the decision was made to go that route. I watch this will great interst as I'd like to take up regular 12 sailing when the kids move on from Cadets in a few years time.