Okay, unfortunately that's not going to fit but that pretty much goes for most bikes. Are there any holes in the cavity to route the cables through the inside of the extension/base bar, to the cavity, to the exterior? Here are 2 examples from other bikes:

http://cdn.triathlete.com/...16/10/LC-Trek-03.jpg
http://www.slowtwitch.com/...etap_junctionbox.jpg

Right now on my P2 I have the blip box mounted underneath my standard BTA bottle cage so as long as there is someway to get the cables to the exterior of the bike I should be able to find someplace (relatively) out of the wind.

I've attached the blip box dimensions too.

Thanks!