The breech end of the solid rib can be filed to shape before installation to exactly match up with any receiver irregularities. The height of the rib can also be lowered by filing the base. It could be a very neat installation with some attention to detail. By the way, the front of the receiver on my gun is a square edge. It is early prewar. Bill, you have given me some ideas for my Remington Model 121 Routledge, which is not in collectable condition.