I tried to keep up with traffic one day in AZ and I was a wreck. I am not comfortable at much above 60. By that I mean I don't feel I am in total control with some of the speed demons on the road. I try to pace myself by my appraisal of my reaction time.
We just bought a Winnie with the V10 and Banks Power, steer safe and all in all a better chassis than our Bounders P30. I haven't been on the road with the towed yet so I'm not sure how it will feel. I do use my GPS for setting the CC and not the speedo. The Winnie seems accurate the Bounder is 3 to 4 mph slow.
55 to 60 is my sweet spot and hopefully it will be for the Winnie too.