This radial vs bias ply tire discussion has caught me off guard.
I always in the past read bias ply was the way to go on trailers, due to stiffer sidewalls.
Maybe not...
I've got 2 new bias ply tires on my Cobra now, they seem to do OK, I typically cruise 75-80, on the straights, out west with that thing using a F150 or full size GMC van.