Just go and buy another one.
I was in your situation 2 mo ago, with the same stock, and for me to modified this one, it took me 1 mo of molding, casting, trying different casting mat, and over all I payd more in casting mat then a new stock.
Finally my stock is done, modified and finished by me, but with hard working time.
it is under 300rum, the one painted in camo.
I did the camo job, that one was very easy with lots of fun.
My advise.... GET A BRAND NEW STOCK.