This is how I should have done it!
Just kidding. I dont have anyone helping me so I tacked the sheet to the firewall and drew the outline from the inside.
When I cut away the flange the metal bowed inward a bit. I ended up having to use some clamps to get everything in place:
Started tacking
I finished all the tacks tonight but it was too dark to get a decent picture. I have about 5 more holes to fill on the passenger side. I am going out of town for a few days though so it wont likely happen until next week.