So how far (in terms of one complete rotation) did you tighten the allen bolt that goes through the derailer body?

Usually a half-turn clockwise would be pulling the derailer clockwise in opposition to the chain's tension, at which point the derailer's cage tension pivot spring would be yielding to the increased chain tension and at which point the bolt on the back side of the hollow mounting bolt should be tightened to secure this chain tension.
Any further adjustment from there would be within a quarter turn, either way, of this position, and secured with the back side bolt.