When using the smith you can place your feet in front a little or a lot or not at all--if you place your feet 8-12 inches in front try keeping them close together as well w/ your toes turned slightly outward-this w/ emulate the hack machine and really nail the vasteus medialus (inner quad head) you just have to keep the weight on the lighter side until development improves greatly and going deep,deep below paralell-(ass to heels deep) and performing each rep slowly and under full control--then you can also place your feet wide,wide and really nail the hips & groin tie-ins unfortunately you can't go very deep but it really works well! and of course you can do foot placement at standard shoulder width about 4-6 inches in front of you but you must remember to keep your head back w/ your eyes focussed on a very high focal point and let your butt kinda stick out so you won't run the risk of damaging your lower back or cause too much forward lean. Front squats on a smith can be tricky but they can be done and should be done if using a smith is your option or your only option-nothing frys the top of the quads better than front squats...best of luck!
