Hey akhawk, I have built 4 boards, but I found that polyurethane blanks (PU) are hard to get, so I made my boards from polystyrene and epoxy,its almost the same as PU, PU boards tend to be heavy and the rails crack easier from hitting from the paddle, polystyrene foam is available from building supply companies, I bought peices 12ft x 4ft x 6"" thick, boards turn out good, Check out this web site for how to do it
www.surfersteve.com/cgi-sys/suspendedpage.cgiI did talk to Shane Steadman from SHANE SURFBOARDS about PU blanks, and he was making his own, might be worth a call he is in Sydney.
Good luck Pete