I have never been a great fan of that many wires under one wirenut whether it is a gray or a big blue. My work around in those same situations is to make what I call a bridge splice. Its simple - four of the wires under one wire nut and four of the wires under another wire nut with a jumper from one wirenut to the other one. Granted you will use an extra gray wirenut, but for me its peace of mind. Or go with the split bolt as has been said. Those cost $6 bucks for the #2 size here nowadays.
