I like the idea of making some lens shades with Fimo, some push on types for a few ltm lenses would be nice. I'd forgotten I had made some lens caps years ago with Sculpey, etc and they held up pretty well until I replaced them with 'store bought' stuff.

I don't think I'll try extension tubes.

On reflection I believe that's too critical an application for me to attempt, I want my lens and enlarger to be perfectly squared and I don't think I can obtain the precision needed with polymer clay with the tools I have on hand. However, you have given me a few ideas to try out. I need to make a battery cover for a Leica MR meter and Fimo should be just fine for that application.