I always thought box squats were better suited as an assist to help if you have issues getting enough depth and issues getting out of the hole rather than stalling about a third of the way through the movement. Depth isn't a problem for me really, and getting out of the hole isn't either, which is why I haven't looked at box squats too much yet. That being said, I might be wrong - you reckon box squats would help with my sticking point?
I was just mulling over the fact that I'm weak as hell off the floor pulling sumo and that's pretty close to the position my hips are in when I stall in the squat. I know the loading would be different because of where the bar sits, but I thought there may be some carry over.