Debian is already installed on and is supported on the Beaglebone. Why did you feel the need to tap into Ubuntu (which is a Debian derivative)? What are you getting out of Ubuntu that you did not have from a plain Debian Wheezy (7.x) image?
Optimization…
It goes back to 2009. With something called jaunty an armel variant built for armv5 instead of armv4t.
It wasn’t till wheezy with armhf, that debian gave users a reason to go back. Which they have.
Regards,