I read here, someone said that he aired up to 46 LB's front and rear, and got great response with a 50 series. I aired up F/R to 45+ and took a back road ride today. The bike dropped into turns and was easy to keep it there, with that air pressure. It's higher than the 42 recommended, but the Z8's really performed.
Kinda like a KLR650. Kawi recommends 22 LB's F/R, a setting that totally sucks, both on and off road. Use 30 in both, and highway travel is smooth and tires last. Off road, around 12/16 LB's works. WTF does the factory know, anyhow???