I bought a WSM 22.5. Put it together last week and starting my first smoke on saturday. I apparently got the 2013 model because it doesn't have the grommet for temperature probes.
Welcome! You have come to the right place, the home of all things WSM. People are finding the notch more convenient than the grommet. Just slide the wires into the slot. Chad Bman's post #12 is the best pic I have seen. http://tvwbb.com/showthread.php?37566-Cutting-Notch-in-18-5-WSM/page2
I have the 18 with the grommet, and I'm thinking of cutting the notch in mine. Once I get done with my old Char Broil gasser Frankenstein mods I'll be looking at the mods for the 18. Wheels, notch, handles, and hinges.