If I understand correctly box squats load the glute/ham by disengaging the hip flexors during the "sit". They work well when adressing the issue of quad dominance. I would not 1RM on a box, perhaps 3-5 x 5 with 70-80%. Use a bench and some plates to stand on so that you're are breaking parallel.
Not a big fan of Hacks myself, however the Front squat and the Overhead squat really tax the core and develop flexibility.