If you don't control light in your bedroom or correctly use a quality blindfold, research shows you could still be trashing your sleep related hormones. From 6 to 12, you have a lot of daylight to block, and just a little bit is enough to mess with you. Also, your body was designed for a year-round average of 12 hours of reduced light.

I've considered a similar schedule. Lots of potential drawbacks to it.