This was a post I wrote about a month ago so it might help
Ok so no offense to anyone who has posted before me but for the love of everyone out there pulling your legs in tight to your chest does not help you rotate!!!!! If you want to tuck tighter you have got to use your ABS. I teach my kids to pull there toes, using there ab muscles to do this. If you think about not letting your hip angle get any smaller then 90 degrees (preferably keeping them at exactly 90) and bring your toes to the top keeping them in front of your knees you should be in a perfect tuck position. A good drill I like to give my kids is just to lay on your back tuck drill, but I give them goals, like laying on your back with your head towards your couch and using your abs to pull your toes you lift your knees to the top of the couch cousin. I like to think of having maybe a volleyball sized space in between your chest and thighs. Using that idea of keeping distance between your chest and thighs (with your feet still in front of your knees) you will feel a natural rotation that when done right will create rotation no matter what. The key is having the ab strength to create that pull fast enough to get your feet around. A bonus to this technique is that you are leading with your feet in front and in a good safe position to land(knees bent, chest over knees, not legs straight chest on knees) I've added some pics to show different tuck possitions
Notice that her feet are in front of her knees making her feet the first thing to the the floor( and yes I know she is on a trampoline but it's just a image of good tuck position. Now lets compare it to some not so good positions.
So in this image it is clear that she didn't set but what you notice is that her feet are way behind so if she wants to land she is going to have to either keep flipping until she over rotates or when she gets her upper body around and finally gets her hips over her head she is going to have to figure out how to pull her feet to the gound.
This is my favorite!! For all those grab your legs and pull them to your chest people out there, this is what I call the grab and pray. Her legs are almost straight, her chest is pinned to her knees and she is just squeezing everything into herself. Now even if she does land it she is going to have her chest still pinned to her knees and be praying that she doesn't fall to her face.
I added this one because it made me laugh! PULL how in the world are you going to pull from this position?? Please, if anyone can explain this feel free to let me know! I challenge you to lay on the ground and pull this position and if you rotate I will give up my cheering days and find a new profession!!
So that is my advice/rant on how to tuck tighter in a back tuck but it's more of a how to ROTATE FASTER!!!!
P.S if anyone is offended or think that I am wrong I am sorry but this is just plan and simple physics