I've cut dados into 2 X 4 construction timber frames (lap joints) for polycarbonate sections for a greenhouse-type structure (actually, a solar wood kiln). I'm going to paint the frames before I assemble, but while I'm at Home Depot to get the paint, I going to get some calk to seal the frame (wood to polycarbonate) and I don't know if your basic DAP polymer sealant is going to do the job. I don't know if polycarbonate requires a special product, and I'm guessing the structure is going to get pretty warm in the summer.

Thanks.