Sure have, I've done them near 17 lbs. Much prefer ~10 but I am limited to what's available at the butcher's. I just top grate the big ones where there is a bit more room.
Rain can getcha if the cooker's not covered. Post hurricanes a couple years ago I cooked in the rain a lot. The deck roof had been blown away and I had nothing to rig up and all the stores were closed. A couple cooks I had to disassemble, dump the water and drenched coals out of the bottom and re-start. Not fun but better than not eating!