I swear I can't get this squat thing down. I seem to be hitting depth now, am able to go atf after a good warmup. But as I approach the hole my lower back begins to round -- I think I've heard someone refer to this as "butt winking" lol. Is this only due to tight hamstrings? I will try and get some vid up, I feel like it is straining my lower back quite a bit and I'm lifting fairly light too.