.while accuracy is commendable, as a keen rc racer, I don't think the AW11 wedge shape lends itself to accurate representation on a touring car chassis. If you made it 100% accurate, it would not fit the posts, cover the central spine or have the wheel arches in the correct places for the wheels. All the replica shells that I have for my 1/12 scale race car (mk1 escort, mini, clubman, starlet, nova, etc) resemble the vehicle in question but aren't proportionally accurate. I think you need to make a bespoke mould, but you need to start with the wheelbase dimensions of the chassis first, work out any areas where clearance is required, then shape it to be a rough representation of the AW11. You'd almost certainly have to lose details like the front spoiler or you'd never get the mould out!As regards actually forming the mould, if you're keen enough you can make your own if you're feeling brave, there's loads of different how-to's out there, here's a couple you might find interesting.
. www.instructables.com/id/Make-a-good,-c ... stic-vacu/www.makezine.com/images/store/Vacuumformer-lo.pdfwww.tk560.com/vactable4.html