The point that I was trying to convey In flying through HKG was that if you stay in the transit area and do not leave the airport you will not be hassled about having two carry-on's. It is the security check after check-in at the ticket counter that gets you.
We spent a few days in Hong Kong as we were traveling to Komodo and got dinged at security, they would not let us pass with two carry-on's. We were forced to check in our roll-on's to DSP. We were flying Cathay on business class.
In flying out of DPS last year on business class I was allowed to take a thinktank backpack and roll-on only after I begged and pleaded with the agent. I showed the agent what was in both bags and told her that I was carrying $35,000 in camera gear that it was too fragile to go in the baggage hole. Luckily she gave in. But in leaving HKG I was not so lucky, their TSA would not allow me to pass through with two carry-on's and my roll-on got shipped in the baggage hole.
I don't believe you have the option to just pay for overweight carry-on's. Either you make your bag comply with the weight requirement or it is shipped in the hole as checked baggage.
If you fly on an US airline overseas you are allowed two carry-on's and the weight is usually not an issue.
If caught at check-in or at the screen point, international airlines like Cathay Pacific or Singapore Air will make you ship your second carry-on as checked baggage, regardless of the weight, even if you are flying business class.