i’m trying to figure out how to make a front bumper. i dont think i’m going to have problems with the outer part of it. but i was wondering about the back side… it would have a lot of holes for screws and bolts and some areas would have protruding plates for more holes.
could i just mold on the backside then reinforce the areas where the bolts would be placed with small metal plates? 
then after that, create the front side then stick the two parts together?
how?
thanks 
from my minor experience most mounting parts are usually expoxied on after the “skin” or bumper is made. Some people only epoxy them in, some people glass or carbon over a flange at the bottom of a mounting nut to the bumper/skin.
so what you’re saying is that i should just make the whole shape of the bumper first while ignoring the mounting parts (mounting for the car) first… and just save putting the necessary stuff for mounting later?
that is what i’ve seen done.
Even on my aftermarket fiberglass bumpers on my 240sx you can see all of the mounting points were done after the original part; bonding a flanged nut with fiberglass. The other mounting points were just holes I had to drill. However, now all my body panels are held on with only zip ties that way instead of breaking my bumper, I snap some zipties.