[Ken / Claudia]

OP has a interesting way to do math. I made that part of RVing really easy, I read the manual about ST tire inflation and did not think I know more or better and followed that guide line. I read the tire sidewall and sticker on the trailer that had the same guideline. That part about RVing is easy.

Only way I have found to end the RV from experiencing road vibration after owning about 7 RVs in 40 years is to not pull it any where. They all do every single one. One could spend endless money on better axles, springs, shocks, hitches, tires and inflation. What about a proper tow vehicle and it's ability's to add to or not, more or less road vibration into the trailer. What about how, what and where you load stuff in the RV. That could play into this whole picture.
In the end a RV is never going to ride, handle like any passenger car or pickup. It's the roads, conditions and the way one drives that will have the most effect on vibration. If you have all the stuff mentioned working as it was suppose to do. Spending 4 grand on upgrades? Likely was a good thing, trying to under inflate tires to get a better ride is silly.