Rob,
You've got 2 options for windsurfing with a SUP board :
1) The new 2009 SUP 12'6" has a daggerboard and mast-track option (no footstraps inserts) :
http://www.star-board.com/2009/pages/products/v_sup.php
2) The Extremist 9'0" is available with a mast-track and footstraps inserts option :
http://www.star-board-sup.com/2008/products/sup098.php
Cheers !
JM