Bought my Sailun’s from National Tire and Battery. Good price and NTB mounted them for me as part of the price. Remember to get them balanced also. I was told they did not normally balance trailer tires but they did when I asked them to! Love the Sailun’s - 20K miles and 4 years and still going strong.
NTB Tire in Summerville, South Carolina has plenty of room for 40' trailers and is where i got my Sailuns. and yes they were balanced.
I would trust the tire manufacturers suggestions and recommendations way more than Keystone who can barely make a functional trailer half of the time. Can’t believe there is so much talk about tires on this forum.