I always put the chamber probe on the same level as the food. The rest of what I'm about to write is how my engineer "out of the box" brain solved temp monitoring issues early on when I first started smoking in my WSM. I'm familiar enough now with my smoker that I just use one chamber probe and put it on the hottest section loaded with meat.
You can use one Maverick and a whole slew of probes. I just label them on the end that connects to the transmitter with tape folded in half. They are labeled "Chamber Top," "Chamber Bottom," "Food Top," "Food Bottom." You can actually swap out the probes while smoking and not lose connection to the receiver.
I just had a well used 6' chamber probe fail on me this week and go in the trash. It's been acting up for a while. You can use a food probe as a chamber probe too until it is time to stick in in the meat. Works fine.