Since you know the loads the tire charts will give you the correct pressures for the best wear, ride and safety for your specific tire. The tire engineers design the tire for loads and speeds; the 'vehicle' engineer 'generally' will provide the pressures for a specific loading case, probably fully loaded as underinflated tires are a safety risk. Overinflated tires will give you a rougher ride and generally the wear on the crown will increase, i.e., you won't get the full life out of the tire, BUT, it will be safe. As noted in the chart from Michelin:
http://www.rvtirepressure.com/assets..._Inflation.pdf
contact the tire mfg (in this case the Michelin dealer) for the applicable load and pressure chart and how to read it ...