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.
2015 Ram 3500 Laramie CTD, 4X4, AISIN, B&W Companion Puck Mount
2016 Heartland Bighorn 3270RS, 600w solar with Trimetric and SC2030, PI EMS, 600w Samlex Inverter, TPMS, Furrion Backup Camera
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.