I'm about to mount mine into my new Temptation. I too noticed the difficulty with the tightness of the nose ring. I took out the rubber and sanded the fiber out a little to that made it fit great. I don't understand why your having a problem fitting the engine unless you already glued in the firewall. I'm thinking the way to mount it is too secure the engine to the mount, then put the engine into the plane with your spinner backplate attached, before the firewall is in. Now come from behind and carefully fit your firewall so it is snug against the back of the mount and it fits like a glove around the inside of the fuse. Its not easy to get it snug but my freinds are so good at it that they only use thick CA to glue it in. Its important that you do it this way to assure that that the spinner is fitting into the front properly. The fuse is molded with the proper thrust offsets. Allow around a 1/16" gap between the nose front and the spinner by tack gluing a balsa ring to it during the fitting procedure. Now mark off the holes where your mount must bolt onto the firewall. Take everything out and drill your mount, attach your blindnuts drill your needed holes and put it back together and then glue in the firewall. Sound right to you?
Another guy in our pattern club is attempting to do the Piedmont/brown mount. I use these mounts that are Hyde knockoffs that we get for around $40. They work very well. I did the mount your doing on 2 sport planes I built last year and they too will work I just don't think they will last. Good luck. Mike