I don't think the eccentric phase is your problem. You sound like a lotta guys I know who rely too much on pulling with your arms. Think of it this way: Exagerate good posture (Chest out, shoulders back, back slightly arched.) Maintain this through the entire set. Now, DON'T imagine your pulling yourself up, rather, imagine you are bringing your elbows down to the floor. Initiate the movement from the elbows, your hands are only "hooks". As for your legs, you may want to leave them hanging straight down instead of curling your feet behind you. It takes a lot more concentration doing all of these things, but it should make all the difference. Let us know how it goes.