Jerry, you have a hitch weight of 590 lbs. According to the fellow in North Charleston, SC who professionally set up the weight distribution hitch for our 2009 25-foot Hi-Lo Classic when we bought it new, he recommended and used 800-lb. bars for our 630-lb. hitch weight. The common theory is to match the proper weight bars as closely as possible to your hitch weight without using bar weight lighter than your hitch weight; therefore, I questioned him as to why 800 lbs. for a 630-lb. hitch weight. Why not 700-lb. bars? It probably was a stupid question, but I knew nothing about this stuff!! He said the product Draw-Tite weight distribution only came in 200-lb. increments. In addition, he said that a weight distribution system provides or allows better tracking at higher speeds behind the tow vehicle. Also, he did not recommend sway control for us because we have on-board sway control via a computer in our 2010 F-250 Powerstroke diesel pickup which was rigged out for heavy duty towing at the factory. I truly believe you can get away with 600-lb. bars for weight distribution which will be easier to take on and off your Hi-Lo along with a power lift.
By the way, you would not even recognize Mt. Pleasant now; it has grown so much since the old Cooper River bridge has been replaced by two bridges side by side; new bridges on I-526, and causeway bridge from Mt. pleasant onto Isle of Palms.
Dee
Summerville, SC