I'm familiar with the Trik-l lineup and many of us favored using them, however they are also now out of business, so we might have been looking for alternates.
But I did a quick look for the Xantrex and I'm not sure I am gettting the full question on what to do?
It appears to me that the new unit does much the same as the old Trik-L but just at a much higher price?
My view is that there would be no problem with charging from two "different directions" but the larger problem that we want to avoid is running both down while we camp.
I would assume they would use very much the same components on the Xantrac as used by Trik-L to keep current from flowing from the chassis battery to the coach battery through their system and without change to the mode solenoid connection.
No actual relay involved but a few simple parts that operate like a check valve on water supply, letting current flow but in one way only.
One of the downsides to solid state electronics is often that they do not want others to know how they build their stuff, so we can only guess what they have inside!
Is there a manual that comes with this? I see mention on the front of checking that but I also see it labeled as very simple looking to wire!
On the Trik-L line it was just a matter of choosing a spot where convenient to get to both coach and chassis battery supply and placing the unit there, which seems to be what is needed here?
I found getting to my solenoid was way too much effort as it was hidden behind a breaker panel, so mounted it in the battery compartment where I had both batteries handy.
Downside of putting anything very close to batteries is the tendancy to corrode more quickly but I was willing to accept that for the ease of install.
But I will also admit to never having seen or used this item, so I may be totally missing the question!
Wake me if I's sleeping??