Nolan has a good idea in just using a single long piece of fiberglass. I checked the price of 6 oz. cloth at Newfound Woodworks. It's $5/yd. That's about $30 to do the deck. If you think about what your time is worth and how long it would take to do the zig-zag butt joint neatly I think the equation has to balance in favor of the single sheet. Beside the single sheet eliminates any compromises in strength.

Intuitively speaking, I don't think it would matter much if you just made a straight butt joint with no overlap. Especially at the bow, I don't think you'd be likely to have the boat break at the joint. You could always add a layer of glass on the inside under the butt joint, just for peace of mind.