Everything sounds good, except I'm not sure what the best arrangement would be for the lightest two between the top and middle rack. They are pretty small hunks of meat, even for flats, so just be SURE to brine them. Flats can be dry, and based on the size, I'm guessing they've been trimmed of almost all of their fat. Grocery stores tend to sell them that way, because that's what their customers want. We like to keep a good 1/4 to 1/2 inch fat cap for smoking if at all possible. For sure don't trim any additional fat off of them. Hopefully someone on this forum will give you some advice on whether you should wrap those part way through or not. I generally don't wrap, but for little guys like that, I'm thinking that might be a good idea. It's been a long time since I've smoked small flats like that. They are challenging to keep from drying out. You might even want to lay some thick slabs of fatty bacon, side pork or salt pork on the top of those when you smoke. Side pork if you can get it would be best, since your brine would contain salt, so bacon and salt pork will just add more salt, although I've never had a brisket that was too salty.
I also have a #1, and I prefer to buy a whole packer brisket (Prime, from Costco). I cut it in half and put the point half on the bottom rack, and the flat half on the top rack. You'll get better, and more meat for the money. A whole packer brisket is going to be around 13-18 pounds (you'll trim a couple pounds of fat off of that), and Costco, Prime will range anywhere from $2.79 to $3.59 per pound, depending on beef prices.
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