crossover use

I know it's somewhere but can't find it right now. I need to know about crossover use. The truck I use for light commercial I will also use in private duty. And how about when I run out of driving time on a commercial trip? Is it legal to drop trailer and switch to private for a trip to grocery store, or drive to visit a friend. Can I have magnetic door signs and pull them when going private, as well as logged off duty? Other than a commercial tag there'd be no external indication of commercial use.

 

I will be company owner. co-owner actually with my brother. we just got our business started last week as Little Sequatchie Transport LLC But once electronic logs are required I suppose I can't control it so easy. Unless the logging system has provision for private off duty use of vehicle. Then again, they do require power to run. Unplug the thing.