Sorry to take an extra day....things happen!
Size calls for a fraction over 3/8's inch. If you do it right (not in the book) cut 6 pieces of 3/8's stainless tubing about 3"s long. Nerl the outside of the tubing, you can use a cut off wheel or even a grinder, and gouge up the outside of the tubes well. Next use marglass/duraglass, or some type of strong body puddy, cover the outside of the tubes and force them into all six holes for the bows. LEAVE about a 1/4" above the fiberglass, when hard grind off the the tubes that are sticking up above the fiberglass. Carefully! Then you can finish off the top when all the body work is being done. Don't worry about getting paint inside the now inserted tubes, when your done painting it is easy to run a dremel or the likes inside the tubes to clean and polish them. I actually drill all the way through the body holes to allow drainage.
ITAL, you do have blocks of wood glued/fiberglassed below the surface of the body/doors where the bows go-no?
I'll follow up with door measurements as soon as they are mounted.
DV