I think they recommend 20% on the high side and 10% on the low side...your 85/75 settings wouldn't last long once you hit the highway without alarms going off......if you are starting with 80 psi on a given day don't be surprised if that changes daily just sitting on the driveway by a couple pounds up and down due to changes in daily temperature, sun on one side , shade on the other, these all effect the tire pressure.....the company's customer service is the best.
Lloyd & Kathy Martin
2018 Forest River Palomino Columbus 383FB
2016 Chevy 3500HD SRW Z71 LTZ 4WD Crew Cab, DuraMax/Allison.
2014 - 38 nights/3500 mi.; 2015 - 66 nights/6260 mi.; 2016 - 44 nights/6106 mi.; 2017-65 nights/6992 mi.; 2018-47 nights/7376 mi; 2019-65 nights/7825 mi.; 2020-56 nights/3917 mi./21 nights booked; 2021-20 nights booked