I have spare solar panels laying around and use them as battery tenders, such as on my pickup, which will kill a battery stone dead in just a week of sitting. My plan is to set one up and connect to the slave port. It may not be elegant, but it will offset any phantom load that may be on the batteries when the genset is off.
I gather that there isn't a better deal on these connectors, so I'll grab the one I found and go with that.
Thanks for your thoughts!