I was thinking of alternate materials for the outer skin of a sandwich walled tear, and my thoughts turned to the signage industry.
Here in the UK we can get an Aluminum composite called Dibond for around Â£100 for a 10x5 foot. Thickness from 3mm, but apparently very strong, very flat, suitable for permenent exterior use, and a factory standard finish in various colours.
It ramps up the cost a little, but by the time you've bought ply, probably sealed it, then bonded on aluminum.... and then if you wanted the Little Guy look, painted it as well.... you've probably nearly spent as much anyway.
Here's a link to the US site:
ps... do I score points for calling it aluminum not aluminium?!?!?