First off, the binghams bow would be low wrist, the Kmag would be high wrist.
I would start by creating a flat surface to glue to. Doesn’t have to be straight, just flat. Then you could either glue in a solid piececut to fit, or multiple thin layers to build the grip out and recontour to your likings.
Personally, I would you the smooth on, but would not put it back in the oven. Smooth on will cure without heat, just takes longer(24hrs).