Use a structural adhesive you will have to check about compatibility of types of resins like epoxy, polyester, acrylic. The texture left by the peel ply will leave a reasonably good bond surface.
However many people suggest you will get a better bond if you sand the surface with some coarse grit, maybe 80 or 120grit or something like that. If you do this be very careful to not sand down to the fibres, only enough to roughen the whole surface. Also make sure you clean the bonding surface with a de greaser before and after you sand it - this can make a huge difference, degrease even if you just use the peel ply surface.
Dave.