How are you going to get the JB Weld to stick to the plastic SPS stock?
If the SPS stock had an aluminum bedding block, then I'd say "Yes, go for it!". But the SPS stock is injection molded, fiberglass-filled nylon. As such it is slick and will flex and twist when you shoot, causing the rigid JB Weld (metal-filled epoxy) to break loose.
My recommendation is to get a better stock and bed it.
JB Weld is a good bedding material, but the stock material is wrong.