C'mon Ed, your an engineer too.
You'd want to know what the margin of safety is too right?
Short answer: Not crazy fast (that's what the jet is for!) but I'd like to know if an el-cheap-o trailer kit with 12" wheels will be reliable at highway speeds. The mountain highways out here top out at 110Km/h, so most guys drive 130...
Based on that, I'd say the tire should be able to run at a sufficient load up to 150kmh till the cows come home.
That's really the only reason I haven't bought anything yet.
Kelly