It wasn't so much an issue with the new stem, it was loose with the old one on there and I thought retightening after putting the new on one would do the trick. But I think you hit on what I did wrong. I realized I tightened the stem before I did the top cap, so it didn't have a chance to compress it enough. Too bad I can't do it right now, but I will try that in the morning and hopefully it should do the trick.