Is it advisable to add pressure to the rear tires due to about 400lbs of cargo I am moving about 1300 miles? Most of the weight is centered between the rear wheels.
I am running 35 PSI front and rear with 225/40/18’s
I don't think 400 lbs will affect the car much. I frequently carry 600+ pounds of people in my car (passengers) and the car feels similar (albeit slower) with them in it... but handling is similar.