Turkey advice

I'm not sure if two 16 pounders will fit not sure if they won't either. The Turkey I recently practiced on I used a roasting pan and had no need for a drip pan but my turkey didn't hang over. I should have used twine to tie the wings down since the tips came out under the foil and got burnt. I did have an issue with keeping the drippings from the turkey from boiling off. I think for Thanksgiving I'll add stock in the pan to keep it from happening again.

With my XL I had tons of room and did t use the AR/WOO combo and just used a baking rack on top of the stone but I didn't spatchcock my turkey either.

And FYI - not room to do 2 birds of that size at the same time...

Direct at 400 raised will take 90 mins + or -. Do one then the other spatchcocked. 

Your only real hope of roasting 2 larger birds in your XL with out Spatching them would be to place both birds in one large pan, indirect.
I would truss them both up real good as you might have to rotate each bird at a half way point to move the inside portion of each bird to the outside. Basically spinning each bird 180 degrees. The twine really helps lifting/moving the bird. Throw some stalk veggies in the pan with some white wine for moisture.
The AR will not work but the Woo should work great...
Even modifying a very large heavy duty disposable aluminum pan would work. Bend/shape it to fit.
The 2 birds will start out touching and will most likely be placed facing opposite directions for better fit. Test fit the birds as soon as you get them still in the plastic to give you a better idea.
Hell, wad up some news paper in a paper bag as a model to get a general shape idea. The last thing you want is a hot Egg and 2 birds that will not fit...not mention a hot wife...lol
I would also plan on roasting them on the slow side. I would keep them at or slightly below 300 because of how tight they will be on the dome.
So plan on close to 6 hours. They can rest tented under foil for a hour if needed. Get a good stable fire before you start cooking. As soon as you toss on that pan your temps will drop big time. Don't try and over compensate right away. Also let you birds rest on the counter for an hour to warm a little.
The small ice pack on the breast meat for 30 minutes is also a good tip picked up on the Naked Whiz BBQ site. Will slow down the breast meat from cooking while the darker meat gets a head start.
Post some photos...

My experience has always been cooking the Thanksgiving turkey on a charcoal fire with soaked Hickory chips or Kiawe (Mesquite) wood (yes I know soaking the chips does nothing, but that's the way dad did it...) for smoke flavor,  on a medium fire (~300 - 350) with no indirect plate.
The bird is stuffed right before it is put on with Chestnut / Sausage stuffing and put in a "special" roasting pan (I'm pretty sure this was just a heavy duty roasting pan that had been used for years on the grill). The legs were trussed with twine, and the wings left free. Any leftover stuffing was packed loosely between the drumsticks and the neck cavity. Melted butter (NOT margarine) was brushed on before cooking. That's it, no salt (well we did use salted butter), no rub, no fancy herb crust.
Cooking was also simple and just involved keeping the heat constant, with a light smoke from the chunks / chips, and basting the turkey every 30 to 45 minutes with both melted butter and the drippings from the pan (we used a small saucepan to choke the chimney, this kept the butter melted and always ready to use). The turkey came off the fire when the internal temperature was at 165, and was allowed to rest.
Interesting tidbit: I remember the first few times we tried turkeys with those new fangled pop-up timers, and we always pulled them off before the timer activated, our theory was that the when basting the juice caked in the timer.

Fast forward 35 years and this year I am preparing to dust off some traditions, I'm pretty sure I will use the same process. Oh yea, here is my stuffing recipe (don't laugh, this is the way mom taught me to make the stuffing)

Chestnut Stuffing

• 1 Bag Pepperidge Farm Herb Seasoned Stuffing mix (the one in the blue package)
• 1 Lb. Jimmy Dean Sage Sausage
• A mess of Chestnuts (in shells) - Think one of those clear produce bags about 3/4 full
• Raisins
• A large onion
• A head of celery 
• 2 Cans of Swanson Chicken broth
• Amontillado sherry

• First cut an 'X' in the rounded side of the Chestnuts and roast them cut up (flat side down) at 425 for 25 to 30 minutes until the shell curls away from the meat. Shell and chop while still warm. (this step can be done the night before)
• Chop the onion
• Chop the heart of the celery (about 2 cups), make sure to include the celery leaves
• Brown the sausage then add the onion and celery and cook until the onion is clear.
• Add the Chestnuts and raisins and cook a few minutes, until raisins are plump
• - You may have noticed that the amount of raisins is unspecified, that's because we just put 'enough' in. Over time I learned that 'enough' was about 1 1/2 Cups
• Add one can of Chicken broth and bring to a simmer
• Add the Stuffing mix and stir
• If required add enough Broth from the second can to moisten the stuffing
• Just before stuffing the turkey stir in about 1/2 cup Amontillado
  Don't worry about seasoning the stuffing (salt / pepper) the cooking turkey will take care of that for you.
• Don't worry about seasoning the stuffing (salt / pepper) the cooking turkey will take care of that for you.
• Don't worry about seasoning the stuffing (salt / pepper) the cooking turkey will take care of that for you.

And there you have it, mom's recipe for Chestnut Stuffing. Over the years I have tweaked it a bit, adding a couple pinches of Nutmeg and Cinnamon (go easy), and some allspice. Adding a few cloves of minced garlic to the sausage while browning. But trust me, if you go with the flow here and keep the stuffing simple (yes this was simple for mom) it will be the perfect accompaniment for your roasted turkey.