Skip- I would still use the Honda 2000. If you have the 4000 watt Xantrex that is running off your 24 volt, when the charging rate dips below 70 amps, you can kick on the Honda. The big reason the Diesel gen wet stacks is no load. Once you get down to the 70 amp charging rate (70amps times 28 volts is 1960 watts) there is very little load on the big Diesel but a good load for the Honda. And since it usually takes a long time for the batteries to get to float, I still vote for the Honda.
I have a 10kw Powertech with no wet stacking problems. When dry camping, start the gen in the morning (after 8am) then turn on both water heaters, that is a 3000 watt load, kick on the coffee maker, another 500 watt load, the battery charger/inverter is running, another 1100 watts for a time, if its cold turn on the electric heat in the bath, another 1500 watts-so right away I'm loading up the gen with 6,000 watts to get it good and warm. If you have an electric block heater, have it on, no matter the weather, when the gen is on-another load. Just suggestions. Good luck, TomC