Joe, I can't quite visualize where along the floor your corrosion is occurring. Also, I've never taken up the carpet or vinyl on top of the floor of my TM. Is there a layer of Lauan plywood (Phillippine mahogany) on top of the aluminum sheet (the upper sheet of the 3" thick foam-aluminum sandwich of the floor)? I would guess that leaked water penetrated the vinyl/carpet and got to the Lauan plywood. With this layer then soaking up the water, the aluminum came into contact with the water. An electrical connection was formed by the water between the aluminum and a bare steel part of the refrigerator (or some other steel or copper part). This created a simple battery. Since aluminum is lower on the Electromotive Scale than iron and copper (steel contains iron), the aluminum was corroded in preference to the steel by the action of the battery. Your aluminum floor was corroded just like the zinc anode of the water heater is corroded. In the latter case it preserves the water heater's components. In the former case it's a destructive process.
You can solve the problem by creating a moisture barrier between the aluminum and steel. For example, consider running the new sheet vinyl under the refrigerator and forming its edges upward to create a pan at the rear and two sides of the refrigerator. That will funnel any leaked water to the front of the refrigerator where you can promptly mop it up. Of course, it will help to locate any source of a water leak from the refrigerator and seal it off. A plastic drain tube from the vinyl "pan" that will take water through the floor and deposit it below the TM may help also. Other helpful measures may include applying several coats of marine varnish to the Lauan sheet and applying a layer of pitch between Lauan and aluminum (messy work!). The outer layers of varnish will minimize the Lauan's ability to absorb and retain moisture. The pitch will act as an additional electrical barrier, or insulator, between the aluminum and steel.
As I'm not familiar with the layout of a 2720SL, all of my comments are just generalizations about ways to prevent corrosion of the aluminum floor. The specific details that may be required to carry out these recommendations will depend on the physical layout of the refrigerator and air conditioner in your 2720SL. You can fix it. It will just take a bit of work.
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