Much appreciate your response.I had to really crank on it and finally got it to line up enough to fit. I have removed it a time or two to work on some things and it fits fine now. It was just really hard to get to line up and even seat together the first time, even with the bb tool and a chain whip. Since then, I can just cam it in place by hand and the hole for the set screw lines up. I'm on I9 hubs FWIW.
Our experience was similar in terms of the initial difficulty for the two clusters to line up; yes, much easier now. That said, even though the hole and the slot for the set screw line up, we can't engage the threads at the 42T. Seems like the set screw will not be recessed/flush to the cog like on other ethirteen cassettes and their instructions. This is frustrating....
I'll report back once we hear from ethirteen. Thanks again...