Oi, I was thinking about doing the same thing to one of my SUP's,but after some good advice decided not to risk it.Bottom curve will be all wrong,rails will be wrong,and it will be way to wide.I went to a windsurfing instructor who sold me a second hand F2 Pheonix 195lt for $400.Its got me up and going and catching of waves(little steering ability) but better than the frustation that would come with a board that was made for a totally different purpose.
regards,
Ian