I am currently in the middle of cutting out rust from a car floor pan, and will need to know soon whether i can do spot welds or do i have to run a bead?

Right now i am thinking that i will first of all:
1.Cut the sheet metal to size.
2.Shape it to the original floor pan.
3.Drill holes through the new floor pan every 1" around the perimeter.
4.Set it in place with a 1/4" overlap.
5.Fill the holes with a burst of MIG.
6.Then seal the seam with sealer.

Does this sound good? I am thinking of using 20guage or 22guage sheet metal.

Any advice or tips/help would be greatly appeciated.

Thanks in advance!!!