[Memorytwo]

I would like to make a fiberglass hood for my Jeep.
what i want to do is add a small cowl or power bump so i can use an old style carb air cleaner. (theyre cheaper than the panel filters, and the V8 jeep has the TB at top anyways.)
And i want to taper the windscreen edge so it hides the wipers and is a bit more aerodynamic.

I would like to make a quick mold of the hood, with out damaging the hood, or painting over it etc. I would also like the ability to style the hood with such previously mentioned mods.

I had an idea of using minimal expansion homedepot "great stuff" foam, as a mold medium. I was thinking about covering my hood in painters tape or yellow masking tape, then spraying great stuff over it.

I prefer having about 2 inches for the power bump, and enough room to sculpt the aerodynamic taper. if expanding foam works, how thick would i have to let the foam be to have rigidity. and what should i do to prevent the resin from eating the foam. also i hear that expanding foam will continue to expand when i cut into it? is this true? how should this be resolved.

I also need this mold to be used on the existing hood, and be able to have the mold "finished" and off the hood within a weekend.

I know this is alot of contraints, but i dont see the point of getting a junk hood just to toss away. Also i dont want to damage my original hood, in case i want to donate or sell it.

Thanks in advance for your help.

-Andrew