You want the shins to remain behind the toes and as close to perpendicular to the floor as possible. Westside is big on setting back when you squat not sitting down.
Overhead Squats are the real deal. Nothing like being a good squatter and having to start with a broom stick to make you feel like a panzy. I managed to workup to 225x3 and 300x1 but the 300x1 was on the pins of a power rack in the bottom position so I didn't have to pop it overhead first.
