It really depends on where you are flying from and who is at the check in desk. I've noticed they the sometimes do make you put your handluggage on the belt to see the weight as well but often they don't. I feel you are more likely to get away with heavies handluggage if you don't have too much over 20kgs in your check in luggage. And not to offend anyone or to imply they aren't treating everyone the same way but i do have the feeling they are sometimes a bit more flexible with certain people.
No real advice for you sorry. Just make sure you are prepared to pay for your extra kgs and if you are lucky you won't have to pay anything. 1 or 2 extra will go through i would guess. More than that... you'll end up paying.I've flown Emirates a lot and they've let me go through with 5 kgs too much but they made me pay when i only has 2 kgs too much. The 2 kgs was flying from Birmingham, 5 kgs from Dusseldorf. It's always a gamble I'm afraid.
Good luck!!!