Just a thought....I have the same ATS and bought that monitor. I mounted mine in the power cord bay. Here's why......when you plug in, you want to know if the power is good on both legs. With it in the power cord bay, you can immediately see if everything is correct. I also laminated the codes and pasted them to the bay door.
You have your Magnum panel and Progressive Industries panel inside the coach, near the dash, that can give you exactly the same info. So why triple the info, use the monitor in the power cord bay where you can check to see what's happening when you're outside trying to figure out why you have no power, rather than run in and out of the coach.
Lastly, there are times when my coach may seamlessly change over to inverter power because the power went out. Being lazy, I didn't want to have to get up from whatever I was doing and check the panels above the driver's seat. On my coach, I have the True Induction cooktop that is NOT powered by the inverter, shore power only. It's powered by a two plug outlet behind the cooktop. I bought a 110 volt LED, wired it to a small power cord and plugged it into that outlet. I had a small brass tag made that says shore power and installed it near the sink where I could see it from anywhere in the coach. With a quick glance, I see if shore power is connected.