I've gone as low as 450 on the gauge. Jarbidge goes better than the B at that flow. 90% of the river is no problem, but parts of 5 mile are borderline too low.
I've run 5 mile at 500 or less at least four times, in everything from a loaded-to-the-gills 14 foot bucket boat to self-support IKs. In both boats, the crux is the same.
I don't think it has a name, but it is the early in 5mile, above Devil's Garden. You will go around a gentle left bend and, too late to stop and scout, or otherwise have a plan B, you will face a river-wide picket fence.
There is one move. It is leftish cutting hard left, almost to the bank, the back right. It isn't obviously the line from above. It's tighter in the IK than in the raft because you can pull the move in the raft. In both boats it's about as tight a move as could be considered runnable.
my first time, boat scouting in the 14 footer raft, a crew had wrapped cat boats on the picket fence. looked pretty epic. made my move but couldn't stop in time to help them.
if you have legit IV-V mank skills, go for it. those canyons are sublime and a little groveling is a minor price to have it to yourselves. hasn't stopped me from goin' back and I'd do a 500 lap again anyday.
Iks might be friendly on the hip-checks than creekers though.