"Vince Anello also experimented with eccentric work, doing eccentric deadlifts with as much as 880. When he returned to conventional deadlifts, to his dismay his deadlift had decreased. Vince told me that anything will make your deadlift go up--except eccentrics. What does this mean? Are eccentrics a waste? Well, yes and no. Eccentric training alone is a waste."
Louie Simmons, "Optimal Eccentrics."
"When doing slow eccentrics with large loads, there is no reason to associate these advantages with the possibility of developing the ability to move quickly and powerfully in concentric work. Lowering weights slowly builds larger muscles for body building but will not assist concentric actions."
"If it is true that an individual can lower 60% more than they can raise, then applying 100% of his eccentric strength, he could hold the bar at any position. However, he would destroy the stretch reflex with heavy weights."
-"slow eccentrics have no place in powerlifting. To build larger muscles, yes. If you want to become very sore, yes. What does it matter if you can lower 60% more than you can raise? If I recall correctly, you must raise the bar from the floor."
Louie Simmons, "Assisted Eccentrics"
Do deadlifts from the floor. Build your strength and skill. Don't do stuff that will distort your technique.
Do rows, stiff legs or Romanian deadlifts from the top. Control the negatives. Build muscles that will increase your deadlift.