[hardk0re]

It wont stick no, but you can sand it and make it rough, when you do this the resin will have sometihng to grip on. I would do what puppet said.

Using the headunit adapter you can plastic weld it inplace.
Cut away the adapter to allow you to be flat with the surface.
Sand the whole front part thats flat
Cut cardboard and fill in the holes you want filled, the cardboard can stay there it will soak up resin well.
Glass the entire front part using fiberglass and resin.
Sand smooth and sand the edges for fitment.

I made allot of gauge pods and everything sticks well to plastic provided you have enough surface to stick to and you sand the surface well enough so it adheres.