Tandem Cycling - Black Hills SD area rides

My wife and I are planning a trip to the Black Hills area of SD this summer. I can see from a little bit of google searching that there are plenty of aff road rides in the area and some un paved Rail-Trail stuff that looks interesting. I'm looking for information on Road rides in the area to decide if we bring the Screamer tandem either instead of or along with the mountain bikes. Does anybody here know about decent road rides in the area? Are the hard packed Rail Trails packed enough for the 20" front road tire on my tandem?

We did an organized ride in the area last Labor Day. We stayed in Custer, SD & did daily loop rides. Custer State Park is a very scenic ride. We also did a loop through the Black Hills that took us past Mt Rushmore. There are many "pig-tail" bridges and tunnels. Lots of up & down. Lots of wildlife (bison, antelope, etc). There was very little auto traffic on Labor Day weekend (lots of Harleys however). I think we stayed in a near-new Holiday Inn Express in Custer that was quite nice and reasonable.

The Black Hills are aptly named. While there are no real mountains, there are a lot of hills. We had not trained adequately and the loop past Mt Rushmore we found quite challenging. I seem to recall it was 70 - 80 miles.

There is also a very popular route called the Mickelson Trail. It is a rails-to trails route that goes for many miles through the area. We did not ride on it but it parallels the highway in several places and appears to be hard-packed dirt or gravel. I think if you look up Mickelson Trail, you should be able to find a map on line.

Good luck.