I have not done it but it is 185 miles. The car is really quite good at estimating on the energy graph. I have left Augusta on the way to Atlanta with a -9% and (watching my speed at 65 MPH) I have arrived with 12 miles remaining. Plugshare (PlugShare - EV Charging Station Map - Find a place to charge your car!) shows several options along the way if you notice you are not going to make it. If it were me I would certainly go for it.
I drove back from knoxville to Murfreesboro with ~85% and still had like 70+ miles. Granted its a lot of downhill from knoxville, but still. With an S70 you should be fine. Its actually 176 miles to the supercharger since its on close side of Knoxville, 198 rated miles according to evtripplanner. If you get a chademo adapter you could even stop in cookeville for 5-10 minutes if you were really worried about it.
If I knew I was in need of driving a route such as that then I'd have held out for an 85. Then again when I ordered 2 years ago there were no Superchargers in driving range of home, and there was no question the 85 option wasn't optional.
I'm currently eyeing Bentwood to Louisville (currently under construction).
$10k for 35 more miles of range just didn't make sense to me. The alternatives are, go for it and cut it close, add an extra 40 miles and go through Chattanooga and use the SC, buy a CHADeMO adapter and stop at a Cracker Barrel. It will probably take the same amount of time either way if I stop. Or, just get the adapter and have it just in case regardless.