Went to get the super single wheels the other day and it turns out I had misunderstood him. He actually had FIVE super single wheels he was selling me for that price ($500)! And two of the tires have enough tread on them to go another 10-20,000 miles.
So when I get back from my upcoming trip I'm going to go ahead and purchase two of the Sumitomo tires (yes they are virgins, btw) and put them on the rear drive with the two older tires on the front drive. Hopefully, by early next month I can buy two more new tires and then use the best older tire as my spare. Since it will already be mounted on the fifth super single wheel I should be in pretty good shape if one of the four new ones happens to blow.
And theoretically, since my trailer runs 22.5 low pro's, if I blow a tire on it I can, in a pinch, remove both of the duals and slap the wide single on it until I can get home.