I set this up this weekend, but in order to get it to clear the 42 tooth cog, the b screw is so far in that the whole derialure has turned by around 60 degrees, and the jockey wheels are miles from the smaller cogs, coming down the cogs the changes are well dodgy.

Has anyone else found the same thing?

Nope, works absolutely fine with nothing special going on with the b screw on both my bronson and mukluk.

Nope. Didn’t need any major b-screw messing for me. Shimanp XT will have an 11-42 cassette, so they’re designed to clear 42

Is the little tab by the derailleur bolt behind the tab on the hanger? Sounds like it isn’t.

10-42 cassette, b-tension screw half way in, no problem.

have you got the mech installed correctly? The mounting flappy bit should more or less point straight backwards. I had an issue very similar to yours a few years ago and the flappy link was pointing back and down around 45 degrees.

see this pic, the small link on the mech between the frame dropout and the rest of the body of the mech should point backwards

mine is fine (XTR with a 10-42 Sram cassette) but when the chain was on the second biggest sprocket the mech’s inner cage would rub on the 42 sprocket, so I’ve had to file/grind a few mil off the cage. Now it’s bob on.

Just been playing around with it. What I had done is adjusted the b-screw so that the dérailleur cleared the biggest cog, before fitting the chain. Which was actually far more than required when the chain was fitted.

Normally I would fit the chain and adjust the b-screw according to the noise when going up to the largest cog, I always assumed that this meant the dérailleur would clear the cogs anyhow. I just fiddled around more than usual, with it not being a supported configuration, and the 42 cog being so bloody huge, rather than just doing it my usual way.

So, lesson learned.