No, the ATI stock for the 9mm carbine won't work on the .40 at all. There's too much difference in the sizes of the receivers, I have one of each carbine in my safe right now. And ATI has no plans to make a stock for the .40 that I know of. And the Dremel fitting is required to fit the ATI stock on the 9mm carbine that it's made for.
And I believe they would make a DANDY h/d weapon! Especially with a laser. But my wife would have a cow if I had a loaded long gun next to the bed, out of the safe. My pistol, she doesn't mind, because she doesn't see it and knows it's usually on me anyway except when I'm in bed.
I personally love the ugly bastards, they're great shooters and a lot of fun. The 9 is actually my 12y.o. grandson's, I had to buy him one because he fell in love with my .40. With a cheap BSA red-dot on them, they're a real hoot!