I agree with Dave, I have been told by several guys in the know on these tires that you better keep the pressure at 110# as recommended by the manufacturer, regardless of the load, or you are increasing your chances of a failure.
I currently have a tire at the Good Year store to replace one of mine, which is showing something that may be the beginning of a slight tread separation from the carcass. They are not sure if that is what it is but are going to replace it.
I have maintained 110# for the most part and have maybe 5k miles on the tires.
Texas Tire Terminal has a 17.5" tire and steel wheel ($175 for tire - $125 for wheel) available which will work on the existing hubs on the Dexter axles which our MS has with the 9/16" studs; thus no need to change out hubs and/or studs (depending on whether you have 7000# or 8000# axles) which is required if changing to the Alcoa wheel since they are hub piloted and require 5/8" studs.
Granted you would then need to purchase a nice stainless steel wheel cover, but they are readily available and still makes your cash outlay near $1,000 less than Alcoa wheels with Good Year tires. Based on earlier research which I did and passed along on this forum.
http://www.herculestire.com/hercules..._s208_s209.pdf the S-209 215/75R17.5 H rated 16 ply
FWIW