when a sub knows her place you don't need overkill. She's surrendered to her situation and knows she must continue to improve on giving her master complete control. It's called trust in other words and she likes his pleasure at her subjugation.
Well, you just have to love soft position bondage like that! There is nothing like a hot girl tied up with her legs wide open, getting fucked silly. Oh, and the occasional pinch and squeal. Really rough stuff doesn`t do it for me, but this is super hot.