Dave,
There are at least two national forest areas in Michigan, Huron and Manistee. We have spent a could of days in each as well as other state park camp areas.
The problem with taking an RV into the dispersed camping areas is that the roads are little more than fire access roads and not suitable for most RVs and particularly not for a TV-TT set. As someone up the page noted, is would be advised that you scout the area with other than the RV. When we did most of this, we had a little 4WD and towed a pair of trail bikes on the trailer that also carried much of our other gear.
Great times, but my poor old body can't even consider that these days.
Matt
Matt & Mary Colie
A sailor, his bride and their black dogs (one dear dog is waiting for us at the bridge) going to see some dry places that have Geocaches in a coach made the year we married.