If you're looking to focus more on the quads, an upright torso position is best.
Taking a longer stride (with a vertical tibia) is more hip-oriented version; taking a shorter stride with a slightly angled tibia is a more knee (quad) oriented version.
So, if you're really trying to hammer the quads, you'd combine an upright torso with a slightly reduced stance length that creates a tibia angle similar to one involved in a standard squat.
A 2-kilogram discuss traveled 140 feet through the air and landed in Dan John's skull. After that, he "rested" for five months. Now he has some interesting ideas about rest periods in general.