I do not attach the shim to the hook, I just fit the piece over the hinge pin and leave it there.

I usually do not break these guns down for transport, and use a full length case.

If the gun needs to be disassembled, I am careful to keep an eye on the shim, most of the time it remains on the hinge pin.
Mike


USAF RET 1971-95 [Linked Image from jpgbox.com]