South Fork sucks!
I gotta put my two cents in on this because the south fork is hands down the worst river I've ever been down. I did it last year at a low flow - just over 1' on the SF gauge. There are at least 10 portages around downed trees. The whitewater is crap - I suppose it could get to IV+ at raging high water, but it would still only be 3 miles in the middle of a 15 mile run. We stopped at a three foot boof to go back and run it again because it was the only thing in there. The scenery is OK, but nothing spectacular, nothing you couldn't find on a river that is actually worth running. Anyways, this thing only runs when everything else is pumping, so I'd recommend you do something enjoyable instead.