shaving the firewall

[Ackattack]

I'm about ready to work on shaving the firewall. I can see two ways of doing this where the heater box was. one being easier than the other....but wanted some input.

First, the hard way: I figure I can cut some sheet metal to the exact shape of the original openings and weld flush. Now on the original firwall there is a slight indention on the sheet metal that I'm sure provides strength, but also prevents me from just tracing around it from the back side.

The second way (the easy way) would be to cut my patch panel to an approximate shape, then trace that onto the firewall and cut on the firewall. This would eliminate this "lip" that's in the factory opening, so it wouldn't be as strong....but does it need to be strong?

So how did you guys do it?