I think that's the problem, it doesn't lock in place under load. It just pulls out.
There are 2 recesses in the receiver . . .
That are lined up with the holes in the stock and take one of my homemade loops rather nicely.
Any load on it in this orientation will just lock it in place.
I still couldn't get it to fit with the stock though, until @Archer s pic showed that it's on a slant.
Still can't get it to fit with the tabs facing forward!!!!! I've made them shorter but still not.
So, lots of measuring and marking and I think you're right, they face backwards but that just doesn't make sense!!!
While I was fucking around with bits of wire, Mr @Archer came to rescue, yet again, and sent me a spare that he had lying around. I still didn't think the tabs went backwards but that's the ONLY way it'll fit.
Thank you for listening to my TED Talk.