Try a Pre-Exhaust Super-Set of Leg Extensions,immediately followed by Smith Front Squats with a couple of ten pound plates under your heels........thank me later,or curse me during the set!!
i dont really like doing doing pre-exhaust before the first base exercise because it makes me so much weaker then. i usually do some pre-exhaust legcurls in the end of the workout.
my routine looked like this(in this order):
4* set front smith squat
3* set hack squat
4* set legculs
3* set mashine legpress(close footstance)
for hamstrings i just did:
4* set legcurls
3* set stifflegged deadlifts
as you see i get some pre-exhaust from legcurls before the legpress. i prefer to be fresh before my first base exercises.
i like close stance cause it give a nice burn in the outer quads and i want more sweep