Bela P. Havasreti wrote:

I always thought it would be neat to move the main gear forward of
the spar on a Navion and stick a tailwheel on the back (has anyone
done this?).

Not to my knowledge. The most radical structural changes I know of
whas turning them into twins and there was a once off built to compete
against Beech for what became the T-34 that was a two place with sticks.
I believe someone actually "recreated' one of these after Ryan scrapped
the original.

The other Navion wierdness was one done I think originally at Princeton,
last seen at Univ. of Tennessee which put a lot of extra junk in and
around a Navion to allow it to simulate other aircraft behavior.