James: Nothing wrong with that plan at all. If you were clever, you would pull the panel and glareshield out of the rear cockpit, limit the upper seat travel and form in a smoked canopy section to the new turtledeck. By doing that, you could retain the rear seat. That way it still retains two place capability, but the rear seat has decent egress capability. The other biggie, is that you would be doing all the work under 337's and not moving to the experimental class.
I would start with forming a buck of the entire deck using foam, carve to the correct shape and then a layer of glass. From there you can do all the main forming on the bench and still keep the a/c flying til it's all ready to install.
If you were considering converting something like a DC-4 to a B-32, then I might laugh and roll on the floor for a few minuets, then we grab the drawings and start scratching our heads a bit.....
If no one dreamed, we would have never progressed as far as we have. You never know what is going to come out of an idea tossed out to a group. It might be something totally impractical, semi-impossible to do or whatever, but it might just be the key to triggering something in someone else to make something positive happen.
Sketchpad designing is fun, makeing parts come together is even more fun, but tearing through the skies in the final result for our friends is the best part