Thanks for the replies, seems no one has had this experience yet.
To answer a few questions, yes, flying CX to HKG, separate ticket on CEB.
I've flown CEB many times, only carry a small (but heavy) backpack, and haven't had trouble with limits. Can probably make the 7kg work (if forced), currently it's 11kg, but includes some heavy items I can slip into pockets or the personal item bag.
Regarding the above post, that doesn't sound too safe to me. Gate manned maybe 1 hour before boarding, if they turn me away, won't have time to make the flight. Logically, I agree with this, and agree with other people's suggested solutions, however, unless someone specifically has experience with transferring to CEB at HKG, I won't chance it.
One question about this? If I use the transfer security line (since I do have a printed boarding pass), and spend some time looking for help airside. How do I go from airside, back through immigration, is that an easy option in HKG?