Brad:

If the shoulder of the handle doesn't match up with the edge of the socket, don't worry about it. What matters is a good, tight, friction fit. In fact if the shoulder is bearing on the edge of the socket, it might actually prevent the handle from seating all the way. If you're not getting a good fit, lightly clean off the handle with some sandpaper, then re-insert the handle, and give it a little twist. Then look at the handle, and look for the dirty spot, which will indicate the high spot. Sand that down and repeat until you get a good fit. Make an index mark on the handle and the socket so that you always insert the handle in the same place (rotationally?).

Most importantly, listen to Bob's excellent advice about never carrying a slick by the handle. Always hold it by the socket.