Hi Rob and welcome to the forum.
You would want to fit a crown that has a recess to accomodate the tube. I remember seeing an explanation up on one of the suppliers websites that explains how to fit one much better than I can explain here. Give me a few minutes (or maybe an hour or so) and I’ll try to locate that page. I think it was up on Caskers site but not sure.
Back in a bit.
Bob