I've never had QR measure my carry-on bags or put them in a sizer, but on a few occasions they were weighed, which is a potential problem for me. I've never had any question at a gate, if there's an issue it's at a check-in desk. So, I try to get BPs in advance, either by using online checkin or, if I'm at an airport, getting a BP at a lounge or check-in desk at an arriving airport. I usually don't check any bags, but I have found that if I check one bag, check-in agents seem less inclined to want to weigh my carry-on bags.