During an auto appraisal, it’s difficult to assess on site whether or not the mid frame rails traveling through the body center are very solid. The problem is that they recess into a cavity along the floorboard, allowing only visual confirmation of solid floor supports through a narrow, 3/8″ gap between the inner rocker structure and rail itself. Having a mirror on a stick isn’t particularly useful in this case. This is especially important on convertibles, as they tend to be more rusty, due to the top leaks over the years. A long, thin ice pick is your best defense to polk around, IF you can get away with it! The best way of course is to pull back the carpeting from the sills and look from the inside.