Auto body repair & detailing: 1954 belair trunk repair, rust holes, floor brace

Question
hello i have a 1954 belair with a couple rust holes in the trunk behind the tires, about 5"x5". i also removed the spare tire well and i want to fill these areas in. i am going to make a patch for the tire well with 18ga sheet metal and roll some beads in for strength. i have a mig welder and need to know how to fit the pieces. my thought is to cut out the rust and fit the patches the same size and weld all flush with a solid weld, but skip weld to reduce warpage. i have been told to lay my patch on top of the cutout hole (flange) but this sounds like a place to capture water. this i a nice car that i have had for over 20 years and will never sell so i want to fix it right. also the tire well bottom was rusty and in the way of where i want to run my exhaust thats why i am eliminating it. thanks for any advise.

Answer
I prefer flanging with a panel flanger, It recesses the patch, making the repair flush and easier to fill. It's stronger, and easier to weld. The extra flange metal also gives the heat somewhere to go, and reduces warpage. The flange shelf will also hold the new floor in place, and you won't be trying to get a few stitches in place while trying to hold the panel suspended in the hole. It's just good sense. I would also plug weld the perimeter with 5/16 plug holes about every 1-1/2 inches. This will maximize strength. I also suggest making some sort of floor brace, rolling a bead in the new panel is not a guarantee that the floor won't oil can. caulk  patches from underneath to seal it up. Cars like this see very little weather, and this repair in this area will last decades, so long as you seal and paint the inside and outside both. Bill