Larry;
I don't believe that there is any DC device in your rig that requires more that 12.0V.
Don't be surprised if Xantrex says to use their Gel setting. The temp sensing cable is going to go a long way to automatically manage the charging/floating volts to keep those Gels healthy.
In our Good Sam chapter, we have a rig with 4 x 6V Werker Gels from Batteries Plus for 400AH. They are charged with a Magnum ME2012 set to Gel. Two of them are claimed to be 10yrs old and were transferred forward to the current rig in 2006, when two more new ones were added. You should expect many years of service from your setup.
Please post what you find out from Xantrex.
HTH;
John