There was a thread over on Standup zone about putting a couple of big keel in the sides and surfing these as a twin/fish.
Here it is:
www.standupzone.com/forum/index.php/topic,22466.0.htmlWorth a read, even if you choose not to go that way. I nearly did it with my 9'10 but somebody insisted on buying it from me before I got around to it.