A couple of questions

You never want to put raw meat over cooked meat. That will lead to cross contamination.

Put your brisket on the top rack. When you are ready to put your ribs in, take off the top rack and put your ribs on the bottom rack. This will prevent cross contamination during your cooking process.

As for cooking between 225-250 degrees. If that is your preference go for it. If you plan on cooking all 3 racks of ribs at a 3-2-1 method you will have some very over cooked baby back ribs, over cooked st louis cut ribs, and possibly over done spare ribs. 3-2-1 method was developed to cook a full rack of spare ribs at 225 degrees. If you are cooking one of each type of rack of ribs, you will need to adjust your foil times/cook times accordingly.

At 225-250 degrees
Spare ribs will take the longest finishing at about the 5-6ish hour mark
St. Louis trimmed spare ribs will take the 2nd longest finishing at about the 4.5-5.5ish hour mark
Baby Back Ribs will take the shortest at about a 4-4.5ish hour mark.
These times are estimates and YMMV.

As long as your target temps for doneness are above 150F internally for more than ten minutes, cross contamination will not be a problem. Bacteria commonly found in food cannot survive past that threshold.


Oh - and the bacteria will most likely only be found if you've held your meat between 40F and 150F for more than four hours before cooking. Uncovered.

I'm an 18.5 WSM guy too. Here's the gig that has worked for me for several years. The meat that will be done first (ribs in this case) goes on top. Use water in the pan and don't even look at the brisket until the ribs are done even if they go 6 hours. I don't wrap so 6 hours is not too long in my case. Once ribs are done to your liking, just pull the top rack off and leave the brisket on the bottom rack. You say your target temp is 200*F. It's not about the internal temp. It's about it being done when it's done.

What do you use to measure IT?
Are you relying on the on the dome thermometer for cooking temp? Don't. It's grill level temp.
What temp are you smoking the ribs and brisket at? I normally run between 250-275*F for both.
What type of wood are you using? Pork takes smoke more than beef. They both take it early in the cook up to about 140*F IT. I would go with Hickory and/or Pecan.

Do the bend test on the ribs to check for doneness and several hours later probe the thickest part of the brisket flat for tender. It should probe like butter.

Good luck with your cook!

On the thing about the sausage, one of my favorite things to do, despite my alleged food snobbery, is to go buy some regular old Hillshire Farms Kielbasa, and toss it onto the smoker for an hour, I do this at the start of the cook, so I can snack on it as the rest of the cook progresses. The extra smoke really makes it taste great. This also works with things like Aidell's Andouille or Chicken Apple, and Evergood Pineapple Pork sausage.