We tried some foam style double back tape, But it didn't want to stick to Spencer's Tank?
There are some very good double back tapes available for molding on cars etc..
I think the best route is Silicon Adhesive..
I added another layer of material just to add a bit more protection. These are beefy
here is a photo.. Parts are textured in glossy clear or Matte. I think they look pretty good either way..