Obviously all of this hinges on keeping the entire firearm clearly well over 26".
Here's my thoughts so far
1. Buy a piece of wood from one of the eBay furniture guys that is cut for contour against the back of the receiver, but not drilled yet, (if it's even possible).
2. Lay the receiver/long bolt shown above on the wood and mark the pathpath of the bolt hole.
3. Design grip shape.
4. Drill hole into front of grip using the lines on the side as a guide.
5. Epoxy a threaded insert into the hole.
6. Thread a long bolt into the insert which has n internal Allen head. (Picture a long, heavy set screw, threaded to match the bolt hole in the receiver obviously).
7. Screw the finish carved grip onto the large Allen head bolt.
8. Screw the grip/bolt into the receiver until it just touches.
9. Finish tightening from the inside through the trigger group hole, if I even have access to the inside of the grip screw hole in the receiver.
I know it was mentioned above that there's no room behind the safety for bolt head, but if I can access the front of the grip screw hole, I might be able to snug it up.
Or not! We'll see.