Emmm, guys... All ribs, 17cm long, not an acrobat, not fat :) But I can do that (with some sort of pleasure). Not all the way, but 70-80%. What I need to say: lots, no, you need LOTS of practice! But there is a problem: you need to max you flexibility to that rate, when you can do it without tons of minutes of preparation. Why? Because if you spend all your strengt to "a little more... almost" - you even can't feel pleasure. You will feel that smth in your mouth. Sooo... Few month and, maybe, you will enjoy this technic.
And this pose is imposible if you don't have 25cm long penis )