i drilled a hole for the screw on bottom, it is counter sunk in the bottom rail which is covered in the picture. Only thing i didnt like was the butt stock holds your head too high to use sights, i ended up slotting the bolts and letting it move lower.
I think you may just have stumbled upon a niche market for your talents. Go patent the technique and sell it to tapco for a royalty. I'm in line for one if the price is reasonable and function is reliable.
I seen this stock but I was afraid it would be too long for my son. I needed the adjustable butt stock. hopefully the manufacturers will get caught up and start making new items.