I have done several wood stocks by using a jointer like this. It kept the cut to be exactly the same orientation as factory, there was really no square thing to guide from on a stock. But I had a jointer handy at work, and it is not a proper use for this tool (and I probably propped the guard open), but it worked great. If you take 1/16" off eight passes nets you a half inch. You can make a mark and sneak right up on what you want.
ETA: I would expect it to cut a synthetic stock even easier.