I don't have a lot to add to this discussion as I have a motorhome and only tow a car behind it. My input would be to weigh the trailer before you buy it. I know it was weighed at the FR factory and I have been at the scales for MH. I know that FR would not make a false statement on the weight of the trailer but I also know that the weight is not always accurate. From my experience I would not buy anything that I tow or ride in that wasn't weighed by me before the purchase. The dealer will bitch about it but to bad weigh it before you sign anything. Then do all your calculations including the carry capacity of the trailer axle's and braking system.
Phil and Dianna
2011 Berkshire 390 RB