Agree with dadmomh. Lots of people here hate the st tires, but they're really the only tires designed specifically for a trailer. The hard sidewall reduces sway, the tread design allows for a sideways "slide" on pavement (not really an issue on a single axle trailer) and the tires are designed for the typical duty cycle of a trailer, that is sitting a while followed by a several hundred mile trip. As far as these tires being limited to 65 mph, I think most people tow under that snpeed anyway. If it's a real issue, the Carlisle rh can be used at s faster speed.
Cool trailer you have there!