EMD360,
It looks you have a mixture of wood along the bottom of some areas with Thermo-Panel walls going up from the wood portions. That, hopefully, means that the bulk of the coach's exterior flat surfaces have the rot proof (?) Thermo-Panel construction.
I notice that your spare seems to be mounted on the back wall? Hmmm ... mine is underneath up between the frame members.
P.S. From your website - you sure do take your Itasca to some neat camping areas out in the boondocks. You aren't afraid to really get out there with it. Kindof like us when we're chasing rocks.