Dual bladder CamelBak

Hi,

My friend usually brings two bottles along on a ride; one with water and one
with sports drink. We've been trying to convince him that CamelBak is the
way to go, and being geeks as well as engineering students, the natural
conclusion would be to buy an additional bladder, fill one with water and
one with sports drink, and mount a drinking tube on each shoulder strap.
Out of curiousity, has anyone ever done this?

Bo