Greetings Jeff!
If what you are considering is having the aluminum facing up (into the
living area), Airstream actually tried something similar with an
aluminum composite floor in the Argosy Minuet 6.0 Metre (1977-79). In
the case of the Minuet, the aluminum composite had some kind of foam as
the core rather than wood and it is attached to the chassis via rivets.
With the composite used in the Minuet, the only two detractions are:
1.) The rivets make floor covering selection more difficult. There are
really only two options that were thought to be worth considering when
my coach was restored - - carpeting or floating laminate flooring with
what amounts to a double layer of the cushion over the floor. I would
have preferred sheet vinyl, but opted for the more expensive Armstrong
laminate to avoid the nightmares of carpeting.
2.) The composite used in the Argosy tends to take a set after a decade
or more of use creating something of a dip in high traffic areas that
can cause some difficulty with flooring.
The only thing that would bother me about the plywood-aluminum composite
that you are considering is how much weight it might add to the chassis.
I have heard of at least one other Flying Cloud owner who's coach is
similar in vintage to yours having problems due to overloading the
chassis as a result of changes made during the restoration process.
Good luck with your decision!
Kevin
Kevin D. Allen
1964 Overlander International/1999 GMC K2500 Suburban
1978 Argosy Minuet
1975 Cadillac Convertible (towcar in-training)
WBCCI/VAC #6359