Originally Posted by
cny-bikeman
Your statement is true, but in my post at least I knew the chain's traction was not the issue, but rather the secondary effect that the wrong chain length might have on interference between the cogs and derailleur cage. It certainly can't hurt to confirm correct chain length. Several of us have indicated the need to check the b-tension screw - we don't know at this point if the OP has tried that or anything else.
The coincidental placement right right after your post, may have misled you into thinking I was referencing. I wasn't, and in fact had I read your detailed post, I might have not posted at all. But many people don't see it import of a floating (vertically) jockey wheel as used by Shimano and Campagnolo. It's one thing to set the
B-screw, off the largest sprocket, as Shimano suggests, but many people forget the other requirement to re-confirm the adjustment using the smaller chainring.
While Shimano suggests a chain length such that the idler cage is vertical ia a middle gear, this isn't critical, as long as the chain is between the maximum (Campy small/small method) and minimum (Sram big/big +1" method) length. Regardless of the method, the B-screw can be set so the RD has decent clearance in all combinations.
Your well explained point about hanger twist is also useful. I touched on this quickly, but you fleshed it in greater detail.