I hope this isn't too late - I've been trying to catch up on things, and have only got to September...
The Nieuport 11 had the forward fuselage covered in plywood which had the outer surfaces covered in linen - you can see the join between the ply and the fabric covering on the rear fuselage on the outside of the Eduard mouldings.
The heel boards and seat were also plywood and the seat was perforated with roughly 50-75mm holes to make it a bit lighter. The heel boards were supported on a tubular structure -there was no "floor" as such, while Eduard has moulded a solid floor. I would suggest that if you don't want to model the entire structure you could simply paint the area between the heel boards and on either side matt raw umber (a dark greyish brown) as the area is pretty much invisible anyway and the dark colour will fool the eye on all but the most detailed inspection.
Even on a camouflaged machine the interior rear fuselage would appear to be a natural fabric as the inside of the fabric was not painted.
The wooden structure was varnished wood, but note that the two vertical struts by the pilots knees were actually steel tubes and were painted a mid grey as was the rest of the iron work. Most early Nieuports came from the factory without an instrument panel as such - the instruments were tacked onto convenient places on the airframe, however it seems that some RNAS machines may have had panels fitted at some stage similar to the one provided in the kit.
Here's a picture of a later model under restoration
http://users.skynet.be/philippesmode...uport23_3.html
Aidrian