I love the 22/Cajun Bandit rotisserie set up. I've used it for ribs (with the Rib-O-Lator), rib roasts, pork loin, etc. and the food is terrific. I usually use my 22" Kettle for rotisserie turkey and chicken and can typically cook a turkey in about 2 hours as described on this page: http://www.rhythmnque.com/2hourturkey.html
Were I to cook a turkey on a 22" WSM via rotisserie, the one thing I would make sure I did was to keep my cooking temperature between 325°F - 350°F. Why that temperature range? I'm not a big fan of having a lot of smoke on poultry and I want the fat under the skin to render. Those will both happen if you keep the temps up and the skin will usually be edible too. If you don't really care about those things, cook at a lower temp for more smoke but the skin will be like chewing on stiff plastic.
I would cook it directly over the coals (no water pan) and with the lid on, damper wide open. You'll likely need to have all the lower dampers wide open too, (maybe not), in order to maintain that temp. If you run into trouble holding temp, invert the door and prop it open for more air intake as seen in the pic below.
If you have the lower grate in place, you can put a drip pan on it instead of letting everything hit the coals. You could even do it put the drip pan in halfway through the cook if you like.
Also, here's the way I rigged a probe thermometer to my rotisserie spit while cooking a rib roast on a 22. Not the slickest application but it worked. You could do the same if you have a small enough device. The key is the run the probe wire inside the metal collar that allows the spit rod to spin in the notch opposite the motor. You can see it in the pic.