On my headset, also cane creek, there is a plastic 'washer' that goes where that gap is. It is just hard plastice so it doesn't seal it but just fills the gap. Is there any movement in that bottom bearing? Does the race push the bearings against the cup? Have you checked that the top and bottom bearings are the same size? If not the bottom ones are likely to be bigger and you may have put the top ones in the bottom bearing.