Read through this thread linked below, but my specific reply is #10.
South Carolina over 26000 lb. Driverís License
I took all the tests and now hold the SC Class F license. As others have also commented, the DMV examiners may or may not be very familiar with motorhomes, and some really may not be familiar with Class 8 trucks although they administer the CDL exams.
Check my link in the post for the locations where the Class F is administered, as some places give the knowledge test but not the on-road test. Go there with your rig and practice on a weekend.