I went through the same process with our 2013 Itasca Sunstar 30T.
It came with 90 all around. The plackard by the driver's seat says 82.
The service manager said 110.
I tried all & settled on 85 as handling best. But it depends on how your coach is loaded. Ours is well under max gross weight with two average size adults & two medium size dogs & normal load. Weighing is best but may be very inconvenient for you so you may not get around to it as I have not. I suspect you will be fine at 82-85 unless heavily loaded.