Yep. All of the p'lifters at my gym have found that a smaller, skinner belt can be pulled tigher to hold the shirt down better and allows for a better arch.
It probably works better for me because my torso is a bit short, so the big belt really hurts my arch.
In my video, I'm using the skinny belt that I bought for benching.
I can assure you that the arch you see is legal. That's actually pretty tame compared to some of the girls out there that have even more extreme arches. USAPL rules...butt remains in contact with the bench. And Bigguns15, get a bigger arch!