Not necessarily replaying just to you, as it looks like you may have come up with a BTA configuration you like, but just wanted to share my own solution in case it helps someone. I also wanted just a standard BTA bottle; I use infinit, so I don't need a bento and I don't want a refillable bottle system there.
I used a Zipp alumina cage/computer mount which I have found really hides the computer well. It comes with adjustable C-clamps intended to affix the mount to the extensions, but that will not work given the distance between the Tactical's built-in aerobar extension mounts.
I just used the main piece which includes the computer mount and used four zip-ties anchored to each aerobar bolthole above and below the position where the mount touches the aerobars. This locks it quite firmly into place. The Zipp mount does not extend across the entire width of the aerobar extensions, but goes about halfway across each at their widest point (since I torqued/angled mine to be able to leave a tiny bit of space between my thumbs when holding the grips). Just be careful not to fully tighten the zip-ties until you have it centered how you want. I inserted the ties through the extensions to not pull on the internal wiring, but honestly it looks like there is plenty of room not to have to worry about that.
Then I attached my bottle cage - I know some people have mentioned not being able to use a Gorilla cage up front but I have not had problems with it and prefer a secure fit. This works best mounting the cage so the bottle faces toward you, and avoids splash onto the computer.
I have never just used zip-ties to keep a cage in place, but I was really surprised how solid this is. There is a tiny bit of play, but it's really minimal and does not distract or impede the bottle access in any way. This totally hides both the bottle and computer behind my arms and places the computer in the perfect place to be able to easily view it and yet not interfere with my hands. I should note that my armrests are mounted at an inner position - my arms thus cradle the bottle which I thought I would mind but I actually like as it simply helps create a more locked-in arm position - but there is another row of holes to mount the armrests farther to the outside if preferable. Also, in case it helps anyone to know, I switched out the stock armrests (which are quite small) to the Profile Design F35 armrests and Cee Gees pads based on what I read in this thread - but be careful to get the right ones if you want to do this. I originally ordered just the standard alloy version, but the boltholes do not line up correctly. Thanks to Damon.L and thugbuster for helping me with this. If you are handy and comfortable with a drill, you can try to drill out the proper spacing, but I chose to just bite the bullet, return those and purchase the carbon version of the F-35's which has compatible bolthole spacing. Too much money but it was worth it to me to just have it work without messing with it. Super-happy with the result. Here is a picture of the finished product - size Large with the tilt assembly.
I also just wanted to say that I had been lusting after this bike since seeing it explode onto slowtwitch nearly two years ago, but hadn't been ready to purchase initially. Dan Kennison answered probably thirty emails and messages from me before I was fully ready (code for wife-approved) to buy, and then answered probably just as many after I purchased and was putting it together. He did it all with every bit of the patience, responsiveness, helpfulness and politeness that every other person who has interacted with him on slowtwitch has attested to. His consistency was a huge factor in my comfort level purchasing, and has done nothing since then except reinforce my faith that I made the best decision. I don't know where he finds the time and the patience, but he has done it without fail. And I freaking love my new ride.
