You have been very helpful Sofa King. Glad you have got yours in. I am going to follow 4129Rs advice and drill out the felt window channel where the rivets go in.
I found it easier to put the felt in, drill the holes, put the glass in, put the frame in, then pop rivet through the holes in the felt.
Putting the felt in after the frame is riveted in place is possible, but I found it easier the other way.
Yes you may see the pop rivet holes in the felt, but who is looking? Only visible when the glass is down.
Plus the holes in the felt does not bump over the rivet.