Plug Weld Floor Pans?

I would NOT trust a panel bonding adhesive on a structural component at all. Small patch panels, sure. But for a structured component on a car, never. I've seen floors and quarters that were screwed/rivoted on actually flex when the car is jacked up. Now i do know the bonding adhesive are strong, but not strong enough.
I would invest in a Harbor Freight MIG welder, scan Craigslist or even Lowes sells welders. I bought a lincoln 125 on CL 6 years ago for 100.00 with everything.