Hi. If you don’t mind, can you please take a quick look and make sure I am not trying to low-bar the SS bar (e.g., bending over too much rather than being more vertical)?
In my quest to feel my quads, unfortunately, even after a “3” session of 5-3-1, and then following up with BBB, I still don’t really feel my quads. 
Thanks.
Looks okay to me.
Maybe ur unique leverages are such that you’ll find it hard to load up your quads. Maybe tempo max depth pause squats with weightlifting/heeled shoes?
https://www.instagram.com/p/B5947qeBai5/?igshid=k7j9l474awj1
If you lean over too much with a SSB you will fall forward.
It’s impossible to extend your knees without using your quads. Quads supposedly have a lot of slow twitch muscle fibres, which may explain why they don’t get as sore as other muscles.