Pretty sure it was later than that. We got to Indian just as the sun had set. Still light out, but sun down. I'd say it was 7:30 when we got to IC.
I just checked my old mail- it was a 9/7/15 launch, from IC, so we were floating from Boundary on 9/6.
I also just checked those dates against USGS data. It turns out it was 1.55', so 530 cfs, on 9/6/15. So a tiny bit higher than I'd said. The day we took out was 1.48' = 479cfs.
Not sure how much difference an inch really makes. . .I'd say knowing which channels not to take and having big boats vs 14'ers makes a bigger difference than an inch on the gage 35 miles downstream.