This for me is mainly a thought experiment but I've done bits and bats.
I'd experiment with cheap stuff at first so you can find what issues that might turn up.
For a start, I'd never cover the front wheel front of the axle because of side wind issues. The body can fit closest along the forks and allow full wheel lock. Don't forget the wheel spray inside!
The material I'd play with would be 4mm Correx; its naturally stiff but it's not so good for compound curves. Stronger bends will need you to run our finger nail along the inner sheet along the corrugations it to bend. If you want compound curves it would have to be like a Zeppilin. A good glue gun works great on this stuff.
However, if you make a structure to support as few sheets as possible then I suppose you can simply use suitable large headed bolts or screws on any suitable shiny plastics.
To make a super fancy shape to fit the bike I suppose the best way is the
polyurethane foam sheet and block route. You build the stuff to the bike and use a sanding block to carve the shape. Keep the hoover close by! Glass the outer surface. Smooth for painting. Take the whole thing off. Dig out the foam and apply more structural glass layers on the inside. Nuts, pegs, clips and reinforcing strips can be glassed in. Glassing completely around foam can make it very stiff indeed.
To help keep the bike clean through all this, I'd wrap it in cling film!
![Laughing :lol:](./images/smilies/icon_lol.gif)