I used to guide on that stretch. Not for beginners. You should be well versed on read-and-run III+/IV.
Narrow Falls is the mean one. You can scout on river-right. If you flip and have swimmers they will wash into the wall that has an undercut. Had seasoned guide lose control going in at 2500. He got the brunt of the pain, and was aware of the undercut, and swam away hard.
I'd say you should be able to navigate Bridges (on Poudre) at 3.5 - 4 comfortably before attempting.
We used to do private training runs in paddle boats starting above Pineview to get us ready for Northgate.
If you do go keep the following in mind:
It is cold water, and most of the run is in a canyon so don't count on the sun to warm you up.
If you get into real trouble there is a guest ranch called the A Bar A. I never had a need to get a hold of them, but they are the closest help. Check Google Maps/Earth for info.
The take-out is river-left behind a small island after the best wave train on the run. It can be tricky to catch if you aren't aware.
Save some energy for the 1/4 mile hike up a steep hill at the take-out.