Rubber - Vinyl Flooring / Carpet in a convertible

A recent thread got me "re-interested" in the possibility of putting the rubber flooring in my 69 Dart vert.

Reason: Gets driven to beach (sand) and baseball fields (clay/dirt) and thought it would be easier to vacuum/keep clean. Most of it gets caught by the mats- BUT the beach sand gets to be a pain... espec with a 7yr old and a dog!!! Its not and will never be a show-car... its driven and enjoyed.
Concerns: Moisture getting trapped between flooring and floor pan creating potential addtl rust issues.

Anybody have this in your car and can share a pic and would appreciate thoughts/feedback?

Heres the link:

http://www.accmats.com/Products/Flooring/Vinyl.aspx

Thanks