Note the old exercise precept: "The body follows the eyes." When overhead squatting, keep a stable & upright position. You can't do that when looking at the ground, and the ground is not the goal. Keep the torso from dropping forward by keeping head neutral & gaze forward or slightly up. Pick a spot on the wall, and stare.
Overhead Squats are as much about stability as it is about strength. Focus on a strong overhead position with the PVC pipe before moving onto squatting.
Strategy & Briefing
The crux of this workout is the Overhead Squatting -- but don’t underestimate the other movements. Move smooth & unbroken through the OH Squats. If you can’t hit an unbroken set, split it in half with a quick rest between sets. Situps should be steady & straight through, with short breaks when fatigue builds up. Don’t push through the burn too much, as core fatigue will affect OH Squats in a big way. Small sets with quick rest on the Pushups controls fatigue best. Again, overly fatiguing these muscles will negatively impact the OH Squats. Once you reach the Deadlifts forget about the OH Squats and finish strong.