If your intent is to clean up the channel, I suspect you'd have (a LOT) more fun and a more productive time by putting a good saw in your boat, getting a very early start, and spending a few extra hours on the river removing trees. If you want to hike and fish, that's another matter.
On fishing: I've done this run many times, and I don't think I've ever seen anyone fishing outside of the first mile, the bottom mile, and a short stretch in the top half where there's a trail down to the stream (but not along it). I think hiking along the stream would be a lot of work and not all that much fun. Some areas burned intensely and you get really dirty hiking in the ashes and climbing over charred, down trees.
I didn't get on this last year, but in 2014 there were only 4 trees to portage (a HUGE improvement from the ~15 before the flossing), and I think most of these could be cut out with a couple hours effort and a good pruning saw.
Here's a trip report from 2014:
Little South Fork of the Poudre Trip Report 06/16/2014