Thanks. I glued it on as a site based on some photos I’d found prior to Stuart’s excellent post. Got it a bit too far forward but I can live with it.
For some reason, making the initial post via my phone has led to an IP block from my home internet connection. Annoying, but now I can only access this site via VPN or by taking my phone off the home WiFi.
Yes, I’ve got the exploded diagram. It does seem as though it should go on the top on the breech but I have no idea where or in what alignment. It doesn’t mesh with the breech top at all.
Great information everyone. Thanks! (I also found a 3rd party AVRE model from Trenchworks that has the side mounting brackets and gunner’s hatches).