Couple good links, top one has some drawings of hand positions. The nice (to some) thing about the moustache bars is that they are fairly "long", so you'd be flatter grasping out front, more upright towards the center, and more so by the bar ends.

link

Rivendell 1

Rivendell 2


So, idea being that you can change your back position more from forward/closer changes, rather than up/down. Kinda. = )