Smoking 2 different sized Briskets in the UDS..

I just did my first brisket on Saturday (which came out great) in my newly built UDS. She held great temps throughout the cooking time. I made a 9lb brisket at 250 for 10 hours mostly due to a couple of temp fibs (which I got under control once I found the problem). I will post a couple of pics next to show you my UDS and first cook.

Anyways, I was originally going to make one monster brisket (15lb) but I came accross another brisket (after buying that monster) that was not measued corrrectly and litterally cost me 1$ for a 8-9lb brisket. I couldn't pass it up, so I baught it and want to make both briskets for Saturday. I did an IMMENSE amount of reading throughout the roadmap and I'm totally hooked. But I didn't catch anything about having 2 different sized briskets.
So I've got a few questions. My UDS has 2 racks at 7 and 4 inces from the top and a baffle plate (pizza plate) on top of basket.

Should I stack on different racks? Will bigger brisket take away heat from smaller brisket (kinda like if baking 2 cakes, don't stack)? Do I add times of a 15lb and 8lb brisket as an approx time table (of course probing gives the final verdict of doneness)? If on same rack, can theytouch? Should I put fat side down on any of the 2? Sorry for so many questions, but I'm sure all have the same answer....I appreciate all the help and love reading all post and vids, especially barfunk (cnt recall his tag at moment)....I dig his style
Thanks

My UDS (it now has a UH logo on front)


My briskett

UGH.....I have a delimma now.....if I place on seperate racks, the 15lb bisket is to big to go on lower rack (top grate touches and leans on it) and to big to go on top rack (lid will not close)....so in essence the briskets must be on same rack and next to each other on lower rack (like picture)....

Is this ok? The pic shows them in wrapper, my guess when allowed to stretch out, the ends might touch.......thoughts?

Great, so I'm ok with doing both (I'm sure I can allighn them better than the pictue)....just make sure probe both...ill give myself good time to be able to make both together.......
Maybe ill take out the smaller bisket early.....say after the staul.....andd finish it in oven
(Thanks jeff)

Anyone have any idea approx on how long this will take? In other words, do I add the pounds and figure a time with that, or do I say the 15lb brisket time will govern (and the smaller one will get done within that time) and approx the time of the 15lber? Thanks for help.