OB:
I tentatively agree with everything you have said BUT, your LondonAire & truck experience using inflation tables was gathered with Michilin's and your 40' LondonAire probably had triple axles? If so, your load was spread over 6 tires, not four.
It isn't my intent to denigrate a product but my previous experience has been gathered using tires of one manufacturer (other than Michilin) and following it's load/inflation tables. My previous trailer weighed under it's GVWR of 13,780 by a full 1,000lbs, ran 2 - 6000# Dexter axles and came equipped with 16" - E tires and over the course of 2 years of usage with those tires, I had 3 incidents of tire shredding & blowouts. I subsequently (upon recommendation from a tire dealer) changed to tires with a less agressive tread pattern from Hancook with same rating and in 2 more years of same distance/roads/loading/inflation had no further problems.
Since our purchase of our M/S 38 and while admittedly using the inflation tables to air up my 17.5's to a safe-for-weighed-load of 115psi using the mfgr's inflation tables and allowing for a margin at that, I have shed the entire tread from one that remained inflated at the 115psi and a tire from the opposite side has developed extreme cupping of tread. The alignment of my suspension has been checked at Trailair's service facitlity.
When the trailer was at Trailair's factory I again attempted to have the tires balanced only to be told "again" that 2 of them would not balance satisfactorily (out of round) and guess which 2 I've had problems with. I have since replaced the badly cupped tire (it resembled the shape of a Canadian Nickle) and upon attempting to get some good faith adjustment from THAT mfgr, was simply told, "nope, your tires were mfgr'd in '05'!"
I have checked the wheel balance while sans tire and it is fine.
I have used an I/R gun since early 03 and have used Pressure-Pro monitoring system since early '06'. Travelling interstates at 65 mph is our practice and it is my belief; all things being equal, these tires should be able to withstand usage under the conditions I view as normal and within parameters of design.
I have purchased one more of them $402.00 Tx included Canadian,
and will post later (after I go outside to check) the weight it took to balance it.