The message I get is your statement that the Lippert frame lasted 10 yrs- of which 7 were with a GN adapter or the Goosebox. And you probably towed a lot of miles in 10 yrs. And the repairs only cost $8k. And there are plenty of frame failures with just a normal fifth wheel hitch.
Unfortunately, past events is no indication for the future. Many of today's fivers have notched front caps and by necessity notched frames. So the frames of today are even less suited to handle additional stress (mine had too much flex with just a normal hitch before Lippert fixed it). Meanwhile there is no end to the 'improvements' in pin boxes and hitches designed to reduce frame stress.
Bottom line it is just a *rap shoot, trailer 'A' with welder 'B' with pin box 'C' with hitch 'D', truck 'E', etc. It is impossible to guarantee you won't have a failure, but possible to change your odds (+ or -) of a failure.
