On my 22.5 WSM, I just drop the 6" long probe down into the top vent hole.
The probe has a 90 degree bend on it that ensures the tip is hovering "in mid air" in the dome. But I'm curious to see what others have come up with.
Meat eater. Woodworker. PS3 Gamer. Home Theater Guy. Beer Drinker.
WSM 22.5 and random cooking stuff used to help form my shapely manly figure.