When I had my Solera (MBS chassis) according to the sticker the recc. pressure was 65 all around. After researching a little bit, looking at the tire charts, taking into account what the actual weight of the motorhome actually was, w/ cargo and passengers, I determined that 65 was unsafe and ran no less than 73 or 74.
Also consider that my new Sunseeker, similar size to my Solera (shorter, same height, wider) , but with essentially the same tires, recommends 80 rears and 75 front. Then again, it will tow up to 10,000 lbs...
2017 Forest River Sunseeker 2250SLE