I just bought a product that may be of interest to those of you (us) with a need to fix floorboards or do some other metal repair. It is called FUSOR 108B Metal Panel Bonding Adhesive that is used in the "trade" to attach body panels such as rear quarters, doorskins etc. I paid about $25 for a 7.6 oz two-part tube of the stuff and I experimented with an irregularly shaped patch of new steel for the floor of my 240D ( corner where the rocker and firewall meet under the clutch pedal).
This stuff meets GM and DaimlerChrysler specs for mig welding and weld bonding - has a lap shear strength of 2250 psi when used on steel.
It mixes much like thin Bondo and smells not unlike the stuff dentists use when setting crowns. In 90+ degree heat it sets up in about 10 minutes but is supposed to allow 40-50 minutes work time at 70 degrees. I don't think I could have patched that inacessable corner nearly as well with a MIG. Another advantage is that is is not supposed to promote corrosion at the bond.
It stayed put today on the ride to work ( I didn't use any rivets or screws) If it lasts I may be tempted to slap a different quarter panel on the car later this year. Additional info is at
www.fusor.com. There are probably similar products out there made by 3M etc.
Rick