Yes, I’ve used a low bx.
From my experience it's the feel that has to be there while squatting. If I've got close to 500lbs on my back while looking at the mirror I can't tell if I parallel , I have to Feel it... Just trying to keep my eyes in my head
With lots of weight I can actually tell where I am in the lift. Most of the time I know I'm not all the where there ,but my brain tells my body to go up.. However if I have someone calling my depth I will listen because there is an outside source. The same with the box.....
I'm trying to train myself here without a box . I know how to do it , I'm just having a mental block when it comes to it.
If that makes any sense to you.