anyone here do custom fiberglass work?

[project89]

i need to modify my cowl hood,and im looking for the best way to do what i need.wether it be done in aluminum or fiberglass.

basically i moves the turbo out from infront of my motor, so now its off on the passenger side and the compressor inlet faces the front of the car.

would be all good as is except i screwed up on a measurement when i built the new crossover for this turbo. it dosent clear my hood

so i need to add about a 1.75 bulge into the hood to clear the compressor housing.simple enough i think but then i got the idea of recesing the hood infront of the compressor inlet to get the inlet out in open air.

bassically i would have to make a u shaped channel that starts at 1 inch wide and comes back about 12 inches and ends at 4.5 inches wide

i have a steel hood i can cutup to mock everything up. and forming everything in steel is not and issue.thats the easy part

but when its done and i get it the way i like it can i use the steel parts to make the molds ?

and if so how do u calculate the size differnce that the fg pices will be since they lay ontop the steel thereby making them bigger or smaller then the steel peice