I believe the 32 front/39 rear is listed for high loads only, or for speeds in excess of 100 mph.

Having said that, I've tried all kinds of tire pressures on my 19" staggered setup, and I find that 32 psi all-around feels "sluggish", with lots of rolling resistance, and does not give optimal steering response IMO. I've settled on 35 psi front/37 psi rear as the optimal cold pressures.

You just need to play around and see what works best for you. As long as you stay between 32 and 39 psi for any given pair, it's safe.