Thanks for the info, entropy1049. I think the problem is with the tube rather than the flat-top since I have the same issue when I put on the bevel cap (just received the Legacy yesterday, so don't have much experience with it yet). I've got a mini tube on order so I can use it with the bevel cap -- will be interesting to see if the same issue occurs with that. I guess there's some manufacturing tolerances with the tube, and mine may be on the far side of spec.
But other than that, loving the Legacy so far!