Those are better than 90% of gym squats you'll see. I see what you're trying to do with the sitting back. If you can do it correctly it is a more efficient squat because it engages the hamstrings. If you sit back correctly as you descend down you should feel your hamstrings being stretched like a rubber band. They'll help blast you out of the hole if you maintain that tension but if you stay upright and let your knees come forward you'll lose that. The problem with the upright squats and front squats is they effectively take the hamstrings out of the movement. That can be an advantage depending on what your after, but for general foundational lower body strength generally you want to target more musculature. The key IMO is staying away from the superwide powerlifitng squats and using an athletic stance and not leaning excessively forward with the upper body.
ya, though, with my close stance + feet neutral + half squat, i get tons of hamstring.. people with shorter legs might have problems getting alot of hamstring in that style of squat, but then they'd be able to squat oly style with good form alot easier.. even so, I get most of my hamstring work from lunges and now pmghr's.. I always took that approach for the people I trained too, that's why i'm so big on unilaterals.. I never could understand how someone could neglect unilaterals anyway, they are so beneficial..
So ya, my formula would be, if you can't engage hamstrings too well in squat, with squat form being "pretty nice", I would:
- hit unilaterals hard
- hit ghr/hamstring isolation hard
- sprint hard
eventually they will become more active in squat regardless of form (to a point) simply from getting stronger.
peace!