I flew Tucson - Cancun and back in June and put all my heavy stuff, including can light, in my carry-on. I was a bit nervous because of inconsistent rules and the inconsistent application of those rules by airport screening personnel both TSA and abroad, but had no problems. TSA did pull me out to open my carry-on in Tucson; nothing on the way back in Cancun. Unfortunately, I think what happens is more dependent on the screener you get than what the rules are. I fly a lot and many of the TSA folk are polite and professional, but many are rude and officious.