Don't know about the dimensions but I did hear a recent story of someone flying back with FR from the continent (possibly Italy) who was allegedly challenged on his 10kg allowance with the claim that it was more than a kilo overweight. Whereupon he placed a 500g bag of sugar on the scales to see that it was coming up as 1.5kg and was hurriedly hushed up and put on the plane. This sounds a bit apocryphal but I was assured that he really did have that bag of sugar with him. (These things can happen. I just came back from Tuscany with bags of chestnut flour!). This is not a jibe at FR by the way as I presume it was local staff. Having said that, are local companies incentivised by airlines to catch people out?
On the subject of Italy and hand luggage I have noticed that they seem to be particularly sharp on allowances there, especially at Treviso in my experience. But, I also noticed that Italian passengers do seem to want to carry more hand luggage than anyone else.