Goodyear has a chart that give weight rating and pressure recommendations for their trailer tires. http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf
The chart shows the weight rating of the tires goes lower with the pressure. Tires that can be inflated to 65 PSI have a 300# to 400# lower weight rating at 50 psi.
That reduction in capacity with pressure may not be the case for all manufactures, but I see no reason to believe it wouldn't, with out a something directly from the specific manufacturer.
I cannot see any reason to run at less than the manufactures maximum recommended inflation.