Got back in the shed after work and did about 2 hours before my tummy got hungry.
I have elected to go with the larger 1/4 scale panels though I did have to cut a bit of the forward end unfortunately. Lost some details but have to be a bit pragmatic.

I will make up a 2.5mm plywood "foot" or in actual fact "feet" as there will be two of them to mount the side panels. Said feet will be hidden by the seat and will allow easy removal.
I had to cut notches into the panels where the ribs go. Panels sit against the fuz side wall so guess I am happy with that.
Side panels and seat are just sitting there in the photos.

Once the sides are sorted then it is onto working out how to do the forward sections of floor. It will be in 2 parts. 1st will be in front of the seat and up to the instrument panel, control stick attaches to this bit then I will do a smaller section in front of the instrument panel that the rudder pedals will be on. This piece needs to be removable easily so I can get to the wing hold on nuts.