You are missing what I'm getting at, or I'm not saying it correctly.
I'm sure that it works fine in your house regardless of the upper floor covering. We are talking about an RV here that is not permanently connected to the power company for electricity so yes IMHO the heat holding capability of a product does make a difference.
Radiant heat does work in RVs and is efficient, but not when the heating elements under what ever floor coverings used are electric wires (like used in some stick houses). Many high end coaches use aqua hot radiant heat where a liquid medium is heated by fuel or electric (the fluid has thermo mass)and circulates under the floor and does not require an almost constant on cycle.
Buster Brown you could install any type of radiant heat system you desire, covered by what ever floor covering, just give consideration to how you will power the system, what the on/off duty cycle would be (heat holding properties) given the materials used.
Do some reading on the different systems available this link is to aqua hot and may give you some ideas. What ever route you go or don't go good luck and do your research.
Aqua-Hot Heating Systems for RV, UTV, RTV