We have a vw passat estate and our normal tyre pressure is 33psi unloaded for all tyres and if the car is loaded with 5 people and luggage they nearer the 45-49 psi.
When we are towing do they need to be at normal psi or do they need to be more even though there are only 3 of us, small dog and not a great deal in the boot?
The advice for fully loaded and towing is nowadays extremely high. So probably you can do with a bit lower pressure then 45/49 . But if you can produce the needed data , I can calculate it for you.
Did it for my Seat Alhambra diesel once and because it had a loadcapacity on paper of 800kg and we had all the things in the caravan, it calculated that I could even use the normal advice pressures for 3 persons and a little load.
But for cars with lower loadcapacity mostly 400 to 500kg the maximum allowed axle load rear is sooner reached, wich needs higher pressure.
Front thoug can be held at normal advice pressure because the weight on towbarr even lifts the front a little, so weight on frontwheels does not high up.
Needed tyre pressure is all about load on the seperate tyres. A bit about speed wich is lower then when not towing.
Front lower pressure gives better gripp and comfort.