On my Wave I have Vinyl. If a calm day I stay nice and dry, but on wet days the water pools on the tramp.
Mesh allows water in, but lets it out fast.
Vinyl from Hobie is very expensive.
Mesh is cheaper and if you stitch them with sunproof thread they will last a long time.
Our store here on this site is a dealer for SLO, Sunrise, Atomic, Super Sails/Tramps and this one built by the Amish:
http://www.catsailor.com/store/pc/viewPrd.asp?idproduct=30624&idcategory=154

Almost all need to be built after ordered, and spring they all get swamped and delivery is slow. The Amish one above are mostly in stock and ship immediately,
RIck