Howdy,Danny..
You may want to go to
Turkey Calculator and see where you are at.
I have heard of people cooking a 23 lb. one in their Smokette.
Most chefs would recommend you stay around the 12 lb. range and do multiples.
You might take a tape measure to the grocery and check some birds against your rack sizes.
Yeah,yeah it sounds silly ,but I have had to do it with commercial ovens and it works.
You might want to consider doing them in batches and then refrigerating as half breasts and leg quarters.
Give yourself a break.
You would ideally like the breast out by 160� and the deep thigh out at 180�.
The biggest benefit to me of brining is the cushion that allows that breast to go up to 165�-167� and the thigh will be up into the high 170�'s and they come out nicely together.
Brined birds will cook faster than you think,but you don't want to be holding up dinner waitin' on you.
Another alternative is to cook the breasts separately from the leg quarters.
I'd do the breasts last.
Experiment with one this weekend,if you are not used to doing them in the CS.
They are inexpensive and gives you an excuse to cook.
Hope this helps some.