Given the Dlask precedent, who knows? Keep in mind that the shortguns are not intended to be fired with one hand. They require two hands to operate. If the firearm were to be deemed a handgun, it would be restricted.
I think that if the barrel were 18+ inches, and oal 26+ inches it would still be a non-restricted 10/22. With a shorter originally made that length barrel and an aftermarket stock, it might be possible to get it a non-restricted ruling, unless it were considered a handgun. I would be very cautious about making up or being in possession of such a firearm in the absence of a definitive ruling. Why not email a photograph and detailed technical description to the CFC legal section and see what they say?