Building your own coaming is certainly possible. One approach can be found at the link below. Although I have never done it this way myself, several on this board have. I'm sure it would look good and function well on most any production kayak. And it's not necessary to use carbon fiber. Glass fabrics will work just fine, and you can tint or paint them any color. As for a seat, one of the best is a carved foam seat. Do it yourself or purchase one. Joe at Redfish Kayaks makes a very nice one (http://www.redfishkayak.com/seats.htm).

: I recently received an '80's vintage plug and mold fiberglass kayak in good
: shape. I'd like to enlarge the cockpit opening and install a new coaming,
: seat and backrest. The original seat and coaming was a one piece affair
: that fit in the deck opening and was held in place with a few dabs of
: epoxy. The inside width of the coaming is 14" and I'd like to widen
: it an additional 2-1/2". Any help or suggestions fro additional
: sources of information would be appreciated.