So I went to the gym to do my "volume day" of squats and thought "OK, let me try some ATG, heel elevated narrow stance squats to hit the quads more" - also with a more upright torso.
Well guess what? 85 kg x 8 reps was HARD... this coming from a guy with a wide stance, heels not elevated, low bar squat 1RM of 160 kg. I'm also at 87.5 kg so I'm struggling to do 8 reps with a weight LOWER than 1x.
If anybody was wondering why the hell I suck at jumping off two feet and why my half squat is so bad well - there you go.
I think in the half squat I'm lifting as much as my quads allow - the same happens with the full low bar squat - I'm limited in both of these exercises by the quads, so there's no difference in between them (not such a big difference, that is).
I will continue to use narrow stance, ATG squats and 20 rep slow tempo leg presses to build my quads (as long as my right knee will allow it).
If anybody has any other ideas it'll be appreciated.