Behind the seat water bottle cage

I don't have one, but I'm regularly passed on race courses by people with them. Actually, I'm  regularly passed on races courses by people without them, too.

Everyone I've seen use one has stayed in the aero position when replacing the bottle back in the cage. 

Aero.........but be careful.

I finally got mine set up... I use the Minoura double-bottle saddle mount on a Profile Tri-Stryke saddle, turned upside down (the carrier,not the saddle, just for you goofballs out there -- so the bottles are horizontal and pointing forward), and Profile Kage bottle cages. I've tried the standard method, with the Minoura, an old Trimble, and the Tacx, and all of them were awkward to reach for the bottle, such that I HAD to get out of aero to do it. But with the bottles mounted as I have them now, it's very comfortable and takes no strange body contortions to accomplish the task (it's mote like reaching under my leg rather than trying to reach back behind my...), and I can stay aero while reaching.

I'll see if I can get a pic posted tonight.

I got a better idea!

NeverReach Hydration System!!!

Please do, I also use the Minoura, on a Fizik, but can't visualize what you did

It took me a long time to be able to stay aero and grab a bottle, and even now I'm careful because I don't exactly hold a really straight line, but can do it without fear of losing control. My first season I would actually pull over to drink!

I can grab a bottle from a rear cage easier than from my seat tube because room is tight in my small frame size, but truth be told, sitting up to drink gives me a quick stretch that I don't mind doing when training; I'd only stay aero to drink when racing.

From looking at the website, I decided I am going to try out the NR system.  It looks like the way to go, plus the late, great Blazeman used this system before he passed away.  I'll be using it this weekend!

I added one in August as I drink a lot and wanted to ride longer w/o refills.

I can get them out easily but getting them back in was more challenging. I honestly think it depends on your body proportions as most men have longer torsos and arms then women.  

I've been only using the behind my seat water bottle holders on the trainer to practice taking bottles in and out. I can do it much easier and will be better once I get outside riding on my tri bike. Aero or not? I honestly can't remember but think out in aero, sitting up to put back.

It's a great system!! I've had it for a couple of seasons without any issues and it worked flawlessly at IMWI this year! 

Thats the drawback of the behind the seat bottles. I can easily reach while in aero (Profile Design type), but do practice carefully! Its easy to lose the bottles though; you'll see all kinds on the race course which alerts you to the bumps.....