Just fabbed up a one piece smooth firewall for my El Camino, last thing I'm trying to do is cut unecessary holes in it. Any tricks of the trade way to cut a smaller hole to gauge closeness and enlage the hole as necessary without being so far off that I now have to patch my new piece for the forward down bars
? I know I can start with a smaller hole. But what's the best way of finding the angle? From front frame rail to the intersection of front cross bar and A Pillar bar.