Just talking 2wd highway travel - not 4wd off-road. The 70 psi is still 10 psi short of max 80 psi at load rating of 1330 kgs per tyre, which is probably 300 odd kgs more per tyre than anyone would load their 4wd to?
With ~150mm sidewall, the less the pressure, the more the flexing, the more...