The S Fork below Cedar Flats is indeed quite easy. A few class IIish things close after the put in, but mostly dead easy.
Pro-tip for the portage around Meadow Creek: hike the east side trail all the way to the airstrip. There's a fly-in campground (not marked on the Cairn map) right off the NW corner of the airstrip, and a short semi-trail out the back of the campground leads right down to the river across from Cedar Flats. Beats walking the road for a few miles.
If you have a choice of floating from Black Bear Creek down or down to Black Bear, I'd pick the upper section. Above Salmon Forks has the better scenery in my book.

