1990 Vanagon GL (second owner)

The Van came with Continental Contact tires.  Maximum PSI is 40
(arg!).  While the tread on all 4 is very good (12K miles), I picked
up a nail that is too close to the sidewall to repair.

I purchased 2 new tires for the rear - Continental Vanco-8.

I can put 36 psi in the front tires (90% of maximum).  What makes
sense for the back tires?  I could go with the door sticker
recommendation of 53 in the back (max for the tires is 65 psi, I
believe).

But is this too great a difference between the front and back for
stability/control?

I will be traveling with 7 people in the Van for the next ~1,000 miles.

thanks