I don't have a sample of the material in hand; but I have worked with conveyor belts.
A lightweight belt is good for bales of hay (ask me how I know). The belt used in quarries for crushed rock would be more substantial.
As an alternative, I propose a section Saw-z-Alled out of a car tire. It's already the right shape.
I like the idea of the passively hinged fairing. In the rear I can see options for longitudinal leaf springs or trailing arms, but I'm not sure about double A-arms.