I had this in Q & A but received no answers...

I received the patch panels to weld into my barracuda fenders to make them have the gills.
There are no directions and I remember watching this on the MuscleCar episode, where he said his patch panels came out to the correct location/measurements. Is there some measurements or directions that have the exact placement for them? I realize the way they are made they are "supposed" to line up on the seams and such, but I just want to make sure they go in correctly the first time!

Thanks