No luck here, except perhaps the luck of finding a near new dolly.
As I said, I had only planned on cruising along at 55 or so. I was really impressed with how well the whole rig handled. I, too, had prior towing setups that were, shall we say, less than ideal. Not this time. 55 ended up being too low in my tow vehicle's power band. I was shifting into fourth too often, and still really losing speed.
55 might be the posted limit for vehicles with a trailer in Cali, but not over here.