Back flying is the best way to learn the sit. When you are learning to fly head up you are going to find that you will relax your legs often and start to cork. When this happens you always go back to back flying then put your legs back down. When you get better and start jumping with others that are learning you are going to do lots of back flying to slow down to keep level with them. Long story short, fly on your back, when you get stable start to put your legs down with that pressure you were talking about. Hope this helps
