I've traveled with a dual 18650 mod in my pocket without issue. (batteries inside the mod)
With two, I would recommend keeping the xcube in your pocket, and the rx in your carry on, with batteries out of both mods and stored in battery storage containers in your carry on. Make sure you empty any tanks you're bringing as pressure changes during take off and landing do a number on them, and you will have a mess.
I traveled this way with Delta and had no issue.