Thanks very much, Scott.  Excellent write-up.  I have a few questions and comments.

1.  The A55 comes with a switch that in the "on" position, turns on the generator automatically if the SOC goes below 60%.  Amel cautions owners, however, that it may not be a good idea to have this switch on since the generator will then run for 2 hours and all kinds of things can happen if you happen to be not on the boat while this is happening.  I've never had it "on" but I've certainly had the "low water" alarm come on because there was some issue with the saltwater intake.    If I had not been on the boat, I might have destroyed my generator. 
2.  Does your 5KW charger get hot when it is charging the batteries?  Where is it installed - in the engine room?  I'm asking because I was on another boat with Lithium batteries and they had very powerful cooling fans for the chargers even though charging was limited to 20% of battery capacity.  The fans were very noisy which for me, sleeping in the cabin next to the chargers, was a problem.  This was in late 2017, the system was designed by Mastervolt engineers and the boat was new then.  Do you have a limit on the charging current?
3.  On the A55, I cannot use my 2.5KW inverter for high current things like the water heater, AC, water maker.  This is done by Amel to protect  the gel batteries, I'm sure, through the wiring of the 230V switchboard.  I was surprised that you didn't mention this in your writeup - presumably the A54 has the same setup for the original switchboard but you are getting around this issue by not wiring your 5KW combi through the old switchboard?  I'm wondering how easy it would be to change the wiring on the switchboard and just add another inverter (in parallel) rather than starting from scratch.  
4.  When you leave your boat for extended periods, can't you just leave the batteries without charger?  If you start them at 100%, it should take many months before they're down to 25%, right?  

Scott, again many thanks for this.  My gel batteries may have another year in them or may not.  It's great to have someone as competent as you doing the major lifting on the choice of battery I will need to make soon! 

Joerg Esdorn
A55 #53
Kincsem, currently anchored by Gibraltar