cardboard mat under the rubber mat?

[knack]

Could be that the fiberboard panels kept the interior quieter and insulated better for the models that were sold as grocery-getters. That stuff was pretty dense - good for sound deadening. Didn't hold up so well when it got wet, for sure.

 

[BlazinCopper]

great info -- I might try to make a new one and put back in it after I get all the holes fixed.