umm i'd suggest single ply non-corrugated matboard or 1-2mm Sintra.
is that what you mean by foam board? foamed pvc sheet (sintra)?
fiberglassing isn't that bad if you replace the glass fiber mat with drywall tape.
Can't imagine carbon fiber would be much nicer to work with or cheaper for that matter.
next time follow antmans tutorial, i did 3 times and every time the shape and flare came out near perfect.
he made using the WoF temps almost thoughtless activity...