Might try BB Hack squats with the heels raised on a 2" board (or BB plates, etc). Better focus on the quads.The bar is held behind the back and the bar (weight) is in more of a direct line with the lower back & legs. Can also think of the BB Hack as a form of a reverse DL. With a Smith you have to follow the path of the machine it's self rather than your natural strength curve/index when using a regular BB. Points of muscle weakness or undo stress can occur when a lift becomes static or can only be preformed in a certain exercise groove. Though a Smith Machine can be usefull, some trainee's have gotten unneccesary injuries through the use of it. When the poundage begins to go up, than the potentional of undo muscle stress could develop. The squat & bench comes to mind when using a Smith, as maybe a concern for some people. Good Luck.