What type of stock do you have on it now?
I'd hate to see you mess with a collectible stock, when M2 potbelly stocks are much cheaper.
Haven't heard mention of the type of barrel band you have on your Stan Pro yet either.
If your hitting 3-5" groups @ 1oo, You may get tighter, but don't expect a tack driver at that range out of a carbine.

JMO,
Charlie-painter777