I'm working a paddleboard design where I hope be using recycled polyester posters for the skin. These are 118g/m^2 which from an online calculator is about 3.48oz/y^2 fabric. Its quite strong, does not stretch much (<5% under 200lb load on 2' strip) or shrink much (<5% under heat gun).

Three questions
1) I've seen a few posts using such lightweight fabric but most seem to be using heavier. But paddleboards don't get as much abuse a kayak (where I've used SOF before). What experience do people have with ~4oz polyester fabric on a mostly flat-water boat?

2) If I find 4oz is too thin, especially for the bottom, would adding a second layer be reasonable? If so should it be bonded/glued together (laminated) before of after application?

3) In other applications/forums (e.g. teardrop trailers) people use fabric but use waterproof glue as a first coat, e.g. titebond 2. It both bonds the fabric to the surface but it also stiffens the fabric But I've not seen anything like that for skin-on-fabric boats. Anyone use glue as a coating, then paint? I remember reading, but cannot find the thread, that said skin movement was important. Is having the skin movable important, if so why?