That maybe a Lipert CYA, but found a one inch crack in mine and had it welded and braced. This was on the outside and I never have had an rear hitch. Behind the crack on the inside was the cross brace installed by Lippert. The welder does many for the local RV dealers. He says it happens more than you think. Seems to happen to owners that put a lot of miles on them like us. Adding more weight and stress to the frame contribute to this? Perhaps or perhaps not. I have the 12k frame and it appears to be just adequate. So just do as you wish and keep a close eye on the frames. Have your fifth wheel weighed to make sure you are not going to go over the weight rating of your frame.