Last night while rolling I was getting smashed (again), and I ended up mounted. After a minute or so of failed escapes I got desperate, and just sat up and performed a movement similar to the sit up/hip bump sweep from guard. Anyway, it worked and he went over, with me in his guard. I have put this down to a lack of concentration from my opponent, but before I dismiss this completely as a bit of luck, is there any validity to this type of mount escape? Is it something that can be made to work more regularly with the right set ups etc?