I think you have it rite by notching out the reciever for the folder. I think you will find one of the holes in the reciever is useable for the rear but you will need to drill the lower holes for the other rivet.
put the trunion into the reciever and put in the rivet. if you need to egg out the holes a tiny bit for the rivet to fit that is ok. once you have the rivet fitting properly , notice if the trunion is flush to the back of the reciever. it is nice at this point if it is flush if not exactly than rember ware it is sitting. now pull it out and put on the side of the reciever and slide in the rivet to hold it in place. position the rear exactly as it was when it was inside and mark the second hole with a small pointed punch. A nail can work fine. now you have located a place to drill your first hole. flip the reciever over and put the rear trunion on the other side with the rivet and repeat. now you have both holes marked. drill them out. DO NOT drill through one side of the reciever and out the other side your holes may not align properly. mark and drill each side. makc shure when you mark your holes the trunion is sitting exactly as it was when it was inside.
after drilling the holes out fit your rear back in and check your alignment. put the rivet back in the top and if you need to egg out the new holes a tiny bit it is ok. now your trunion is ready ti fit the notch for the folder.
here is how it notched out for the folder. with the trunion in the reciever and with the two rivets stuck in the holes NOT CRUSHED . I marked the notch inside the reciever and removed the trunion. now I used a die grinder {like a dremil} and cut out the notch along the line. now I put the trunion back in and used a small file to file away the line and get a nice fit. finish up with a small FINE file and it will end up nice.
Now for the release button hole. I did my best to mark the reciever on the center of the hole and drilled a small hole then checked it's location. then worked my way up in hole size and finished up with a small round file because the hole did not start exactly centered. some extra time will result in a nice round hole.
now you are pretty much ready to assembel the rear and rivet,
Some guys will recomend you start from the front because you can adjust the dust cover fit with the rear if you do it after. I however have never had the dust cover issue. you may consiter dooing the front first but honestly I have never had a dust cover fit problem. this should give you a place to start dooing the rear when ever you decide to do it. good luck and happy building
