Good news, glad to hear you got it sorted out.
In real life, the 'skeltonized' stock on the AI-AX folder is pretty wide (like a ruler) its maybe 1 inch wide (guessing, don't have a ruler). In any event, the SIG is about half the width. Thats where AI gets the beef (rear heavy) and SIG gets lighter.
Keep in mind, when you go to use a rear-bag, AI=better because alot more surface. In particular resisting the twist force (equal and opposite to spin/ drift from rifling.) But the SIG is usable with a good "pinch" technique (don't overfill bag).
They were replacing hinges, without asking, during the round trip for the trigger fix. It was posted upthread.