Boondockers are supplied by PowerMax. See the Boondocker link here
http://powermaxconverters.com/ For 6v batts you want the adjustable voltage version so you can meet your battery's specifications for charging and floating, and also to get the fast charging by being able to stay at the set absorption voltage for your entire "50-90"
The Honda 2000 can run a 60 amper no sweat but might struggle with the 75 amper. Go for the 60 so not to waste gen time with only a 45.
I have been using adjustable voltage PowerMax converters since 2011 and am a fan. In some scenarios, some campers might prefer the PD style with the Charge Wizard. Lots of PD fans on this forum. If you get one do make sure to get the version that does 14.8v which your 6s need.
