I am able to calculate it with use of my made spreadsheet.
In this I use an even saver formula then the European tyre-makers use, wich on its turn is saver then the American tire-makers use.
I also add a reserve for maximum reserve with still acceptable comfort and gripp.
But need more details, and those are next.
From Vehicle ( I asume motorhome because of the comfort you want, but correct me if I am wrong).
Weights on seperate ends if loaded the way you use it, so with persons and loads in it.
Configuration = number of axles rear and number of tires on the road.
Speed you wont go over for even a minute in your use.
From tires next:
Maximum load of tires or loadindexes. for single and dual.
At pressure or loadrange ( probably LR D).
Maximum allowed speed of tires , mostly give as letter, N is up to 140km/86m/h and Q and higher use 160km/99m/h as speed for wich maximum load is calculated.
Give that and I will give picture of my filled in spreadsheet with some more information.
Will give a highest pressure to fill with still comfort and gripp.
But also a lowest pressure for the maximum speed you give at wich tires still are save , so wont get to hot and damage by driving that speed.
Greatings from a Dutch Pigheaded self-declaired tirepressure-specialist.