I've never used these extensions, but I think its a safe bet to say you should invest in some longer screwes. I know for my choate SKS stock the extensions that come with it, do come with various length screws. And I couldn't imagine it working without them. On the other hand though, if the screws you have still grasp enough wood to hold it sturdy, I'd say go for it.
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die standing and go down swingin