Start on your toes before you begin your pass to eliminate tumbling "flat footed" (heels should never touch the floor).
Lead your entire pass through your wrists and fingers. In other words, in your round off hurdle, and out of your RO and HS into your trick, your arms/shoulders should be extending away from your ankles as far as possible and in the direction you are tumbling.
Think about the best double down cradle you have ever seen, the flyer lifts up and away from her group, with her ribs lifted as high as possible like shes sucking in her stomach; not down and in like an ab contraction. The twist will be faster and so will the pass if everything lifts away from the floor as stretched out as possible as opposed to trying to "Snap it" which can result in low skills and painful ankles. :)