Fiberglass mold making

[BigBlockOlds]

I'm in the process of making a few side rockers for my car using fiberglass. I'm applying clay to the side of my brothers car for mock up and then will be using it to make the fiberglass pieces.

My question is if there is a trick to getting an exact duplicate mirror copy of the pieces for the other side of the car?



Or am I stuck eyeballing them to get them close?
Thanks,

[63SW]

This isnt my area but i have a ideal or two that could help- Possibly.

1 is that they have a tool you can use to make sure that the shape you have MATCHES the shape you want.
YOU CAN GET IT AT HARBOR TOOL and FREIGHT in small and LONG.
I dont know what ist call but it has 100s of pins side by side and when you push it up aginst a object , the pins slide and comform to that item.
Then you can use it on the opposite side .

OR , Templates always work well.
Once you have the desired shape made from clay , lay out pieces of constuction type paper to form the rocker you have made out of clay.
Take that and reverse it and mold your clay until it fits correctly on the other side ?

Just my thoughts and ideas for what its worth ! hope it helps