I have a Nexus 7 speed hub with 19t cog and a triple chainring.
Experiment: Using a rear derailleur to take up chain tension; the hub shifts fine in all gears and the the triple shifts fine. It all works well in that respect.
Issue: I have resistance in the hub while back pedaling that leads to slackening in the top run of the chain.
Question: Is this resistance normal on internal geared hubs or should it spin while back pedaling as freely as a cassette based hub?