Did you upgrade the sub-frame bolts ?
Your load looks like the ultimate strength test for the sub-frame and many have failed with less loading.
Good luck in your travels.
RR's Catnip Hill to Peoria ___Loopin' Seattle to WestFest
It started with some beers __1500 miles to the Dentist
Skeedaddle to Seattle______ A 30 year old on a Three Flags Run