MM,
One way to keep the weight down is to first apply a coat of clear dope to the wood, sand with 400 paper then layout the fiberglass, either 1/2 oz or 3/4 oz, (some feel the 3/4 oz glass uses less resin and ends up lighter). Spread the finishing resin and smooth out any bubbles, make sure the glass if fully wetted out. Next take a stiff playing card and scrap off as much of the resin as you can. Don't let any of the resin pool, the whole part should look a little dry. Once this is cured apply a second coat of resin and again scrap off as much as you can. Once cured, sand smooth with 400 paper and you are ready to finish.
Best, DennisT