Wow, I just checked the cabin baggage allowance online and had no idea CX technically has a limit of 7 kg for Y and PEY. I've never had my carry-on (which is a standard international compliant rollaway) weighed by CX. I think the only non-LCC airline that has ever forced me to weigh (and subsequently check) a carry-on was LH.

7 kg really is quite limited-- for rollaways, the empty bag alone would probably take up 1/3 of the allowance!