Dana,
   I have a IVP but maybe this is pertinent.
   I started with a big concorde 24v and two smaller 12v.
   After sulphating my concorde battery I became seriously unimpressed with aircraft battery technology and switched to two Odyssey 625's and put them in the battery box instead of the concorde.

   If I had it to do over again I would go with all matching odyssey's and downsize my main box.
   Then you can rotate the batteries through (e.g. put new ones in the standby system and rotate to the main system)

   Colyn