At 78 feet there is a good chance you'll get a ticket before you get out of Utah. One of my workmates got a ticket/fine last year just outside of Price Utah for towing a 5er/boat combo that was at 69 foot.
Note that B.C. seems to have stepped up safety checks of vehicles on its highways. Early this month on a trip from Vancouver Island to Yukon we went by 5 or 6 safety inspectors; weren't stopped but were stopped last year just outside Prince George.
This month we were stopped at a safety check in Yukon, at the junction of Hwy 37 and the Alaska Highway. No issues for us, fortunately. It wouldn't have been a good spot to be stranded while seeking a way to comply with towing/safety regs.