Perhaps you should Google and see if you can find the properties of PVC.
Possibly you could find a copy of Modern Plastic Encyclopedia at work, it has all plastics.
PVC is really quite flexible, it is deceptive just trying to flex a small length because it appears stiff.
But I think a bigger drawback could be thermal expansion, this is much more than any expansion with a wood based structure.
I would suggest you look into something like the Baltic Birch plywood that is available at a (semi)reasonable cost.
An open mind is a virtue...so long as all the common sense has not leaked out.