You were close. Chainpur is 30+ miles upriver of Dipayal, where the road crosses and where we started. Looks like the river is class 4-5 up there.
We flew into Delhi and took a a train East, crossed the border at Banbassa, then a combination of taxi, rickshaws, walking, horse cart, jeep and bus got us to the river. We both got a stomach bug. A dose of Cipro cured me.