I bought some Revines off a guy in Atlanta last week.........chit chat.......
I was telling him that I was looking for a tow dolly to chase after XJs and he warned me about an incident that happened to him years ago as he was doing the same. He was turning left across traffic while in a decline, towing a XJ with an XJ on a dolly, he could not come to a complete stop as the weight of the XJ behind him forced him into oncoming traffic and caused him to jack-knife in the oncoming lane. The weight of XJ and dolly was well within the 5k limit of the class three but exceeded the braking power of the tow XJ brake/weight ratio.
I told him that I was looking for a dolly with electric brakes:)
This is exactly what I was taking about earlier in this thread.
As for a 4-6" drop bar? If the hitch is indeed rated...........I would not worry about the drop, you'll be fine.