Our Lexington 283ts is the same as your Concord, same air bag system.
Never run with them empty, keep a minimum of 10-15 psi. Max psi is 100.
You need to experimint with different psi settings until you find the most comfortable ride. Depending on your loaded out weight, and how much is on the rear end, I'd start at 50 psi, and go up or down in 5 psi incriments.
Be aware, the air bags themselves are small, and it does not take any time at all to hit 100 psi. When you add air just add it a "blip"...maybe a second or two at a time. It would probably take no more than 10-12 seconds to go from totally empty, to full 100 psi.
For info, I setteled on 60-65 psi on our Lexi. That psi along with the Bilsteins I installed, give me a firm but comfortable ride.
Steve & Cheryl + Charlie & Casey, our furry kids.
2012 Forrest River Lexington 283ts
Toad, 2013 Subaru XV Crosstrek