HK 91, MARS CETME, HK 93 comparison
The recoil spring / rod assembly and buffer is slightly different between the HK 91 and CETME and seemed to prevent the CETME stock assembly from sliding fully into place on the rear of the HK 91. I gave it a good press against the floor but didn’t wanna go banging on it just cause I didn’t wanna ding anything up. Interestingly enough with the HK 93 bolt assembly removed the CETME metal back plate easily slid all the way on to the rear of the receiver and could have been pinned in place. It looks like it would be pretty easy cutting to remove the extra pin hole, you have me thinking about doing up a set of furniture myself. Obviously you would need to change up the recoil spring bits to work with the HK 93 style but that can’t be too complicated.
It looks like the screw hole on the CETME handguard (once slightly shortened) and the pin hole on the HK is in same place. It might be worth trying to just keep the front screw attachment and put a bushing in the pin hole on the hanger to make everything nice and tight.