I have recently discovered the weight distribution of these vehicles, and with fuel onboard, it is about a 50/50 ratio between the front and back.
I find no justification for increasing the pressure in the rear tires. The recommended elevated pressures from BMW accommodate two rear passengers, significantly increasing the weight in the rear.
Consequently, I will undoubtedly maintain consistent pressures throughout; the only task remaining is to determine that specific value. Your 32 psi figure, Alan, appears logical to me.
I have utilised Toyo Proxes T1Rs consistently after experimenting with all the leading brand performance tires throughout the years. I consider them to be excellent, and they can be had at far lower prices than prominent brands if one compares options.