ReefedOne:

Yea fiberglass Performance boxes are $600 now. TOO high. Here is a link for three box designs. Two out of pipe and one out off plywood. You could probably substitute aluminum sheet for plywood on the plywood design. Have someone cut it for you and either use bent strips and rivets or weld it together.

http://www.thebeachcats.com/catamaran-repair-tips.html

Good Luck

Doug Snell
Hobie 17
www.tcdyc.com