My old Astroscan also lost the resiliency of its foam "mirror mount." Years ago I took the circular spring ring out from the optical window, but the window wouldn't budge! It looks to me like it's glued in place. Am I missing something on removing the window? Mine is an older model made before they started supplying the scope with an RKE eyepiece.
Since the scope was so poorly collimated with the sagging foam, and I couldn't get the optical window out at the front, I did what any 10-thumbed do-it-yourself-schmuck would do. I took a hacksaw to the globe and cut a hole big enough to get to the mirror. Out came the steel spring ring that secures the mirror and out came the saggy foam and mirror. Now it's time to recoat the mirror and put it into a conventional tube (I used a shipping tube). I bought a smaller secondary from Orion and used a mirror cell design from a book. Once the mirror is re-coated I'll put it all together. But hey! If someone can tell me how to get that optical window out, maybe I'll remount the mirror in the original body, patch the old globe and have another go at using it as originally designed. I got some amazing views from that scope, including the best of the Andromeda galaxy I've ever had (Joshua Tree National Monument after a clearing rainstorm).