Gene, Our RV manual is at the RV storage site, so I cannot look up what is said about the 'emergency start' switch that is somewhere on or adjacent to the dashboard...Does this switch serve as a 'jumper cable' between the chassis and coach battery?
What are the cons of using those fancy maintenance-free batteries for the coach? As I recall, they are smaller than conventional, so maybe two could be squeezed in the space provided for one conventional type.
On edit:
The chassis battery is typically not deep cycle as is (I assume) the coach. One would tend to use an inverter w/ a deep cycle storage capacity, right?
Also, after posting, saw this search result about AGM batteries in RVs
http://www.rversonline.org/ArtAGM.html