A new stock isn't an option right now. I just bought a used US Optics from a buddy to put on my SPS Tactical, and I'm tapped out right now.
As for JB Weld sticking ... I'm not too worried about that. JB Weld will stick to just about any porous and non-porous material and adhere properly. If it will stick to PVC, ABS, and Delrin it will stick to my injection molded stock.
At any rate I plan on assuring a mechanical bond to the stock by drilling several 1/4" diameter by 1/8" deep holes at different angles in the material to assure adhesion.
I also plan on degreasing and cleaning the interior of the stock with Denatured Alcohol prior to the application.
Also, I only plan on filling up the recoil lug area and the areas where the receiver meets the stock. The barrel will be free floating.
For the record. The shrink rate on JB Weld is 0.0001%.