It's very common here. I do it all the time but my hoe only weighs 40k#. I'm at about 74,000# when loaded like that. I can legally put a 50k# machine on my triaxle trailer (weighs 11k# empty). If I had a 20tn hoe (they weigh about 50,000#) out back, I would gross around 84k#. That is legal, in my state, as I can go 85k on secondary roads. I think that the 80k# rule on the interstate is on 5 axles (I've seen B-trains on the interstate in Utah- I doubt they are 80k#). My set-up has 6 axles. Regardless, my tow unit weighs in at about 12tn, and I often run the trailer at 23tn (excavator, trailer, and compactor). I have no issues with the trailer being heavier (almost double the weight). It tows like a dream. Very stable.