We just drove south pulling our 29 foot Prowler and followed the special detour from the bridge in Dave Hunter's book, "Along Interstate-75." His special detour (not the official MDOT one) only took us 5 minutes more and was an easy drive with the trailer.
Incidentally, Mr. Hunter has a companion website for the current edition of his book, where you can download detailed coloured maps of the website.
Several year's ago, "Along I-75" also saved us hours when he posted his own special detour to get around the famous Tennessee rock slide which closed the interstate for several weeks.
He was aware of a paved logging road which paralleled I-75 all the way north to the Kentucky border - only the locals seemed to know about it.
Very little construction for the rest of the drive except for a few sections in Ohio. Most of the signed construction sites appear to be nighttime lane closures but all is open during the day.
Diana.