You could always mold, cut and tape the Coroplast to your liking (using a few thin strips across the inside for strength). Then-once you get the perfect shape-you could harden it with a few thin layers of Fiberglass mat and epoxy.
The resulting composite is a little heavier and slightly less flexible, but gains quite a bit of durability...the only downside is that you'll need to sand, apply Glazing Putty here and there, and maybe a few coats of Sandable Primer for a great finish coat.
I made a REALLY cheap boat this way- PVC frame for the skeleton, Coroplast for the shape and 2 layers of Fiberglass for the outer skin. The exposed interior PVC was then covered with 'socks' of Fiberglass to reinforce the entire structure, and then a single final layer of Fiberglass over the exposed Coroplast interior. The remaining Coroplast was then attached to the floor with Velcro fastenings for a cheap, removable flooring. My former neighbor liked it so much he bought it off me for $500...not bad for $80 and three weekends of Elbow grease!
Now I wish i'd snapped a picture...Oh well.
Sometime after I earn my Certifications and get a decent career off the ground, I intend to construct an EV Trike-my inspirations will be the Twike and the City-El vehicles, minimalist design and sturdy construction. So far it looks like i'll be using a chassis of light steel bike tubing, multiple layers of Coroplast and Fiberglass for the finished outer panels, cut foam layers covered by Fiberglass for the interior. With any luck i'll be well under 800 lbs with batteries, motor, electronics and motorcycle wheels/suspension cradle.
Mind you, ALL prototypes look good on paper...
