I'm using a 6600 rear mech just fine 1x10 but with a narrow-wide ring.
I'd expect problems if you're using the regular 39t inner from a 2x setup, unless of course you just leave the f mech in place.
I've got a raceface N/W in the front. Did you change the tension spring (not in the factory hole/slot) in the mech?
The B screw? I didn't. I don't think it does anything unless you're on the capacity limit of the mech. I had a play but I think you need 30t in a short mech for it to be useful (mine is a 12-28tt cassette).
@who22 started
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I'm using a 6600 rear mech just fine 1x10 but with a narrow-wide ring.
I'd expect problems if you're using the regular 39t inner from a 2x setup, unless of course you just leave the f mech in place.