Treads like this concern me. Basing tire pressure on YOUR coach on what others with different coaches, different weights will not get you the correct answer for YOUR coach.
Please:
Best-- get individual wheel position weights. Using the heavier wheel position on each axle, go to your tire manufacturer's Inflation Table to determine the correct MINIMUM PSI for all tires on the axle.
Get axle weights. This ASSUMES perfect left/right weight distribution which is not likely. So you will need to add a "fudge factor" to account for left/right imbalance.