In your other thread you indicated your motorhome calls for 75 PSI front and 70 PSI on back.
The Michelin table from post above indicates that the 75 PSI in front is required in order to reach the front suspension's 5,000-pound rating. Because you are only 540 pounds from the 5,000-pound maximum rating, I personally wouldn't drop the pressure much if at all. From a practical standpoint what would happen if you add a little extra load or bring some friends with you? Are you going to re-weigh the motorhome and adjust air pressure every time you make any change? I wouldn't want to.
Your "average" rear load of 3,520 pounds per dual would suggest you could run lower air pressure but what would you gain? Beyond a little softer ride that is. And perhaps slightly better tire wear? If you added load or wanted to tow you'd be back to adjusting pressure. It appears the 70 PSI was chosen to closely match the rear suspension's load capacity (assuming you have an E-350).
Also keep in mind that motorhomes are not necessarily symmetrical in load from side to side. If your front axle weighs 4,460 pounds, it could be 2,230 per front tire, or it could be 2,460 on one side and 2,000 on other. This would mean you'd need every bit of the 75 PSI in front to cover the side with greater load.
Unless I weighed all four corners and was certain I wasn't going to add load, I would personally stick with the recommended on RV.