Slowing the footwork is never wrong. Make sure that you actually slide at the foul line, a tad before you release the ball, and keep your upper body upright (square shoulders). If you bend forward, either through an open shoulder or from the wasit (due to an unbent knee!), you shift your body's CG away from the cventerline and yiou simply cannot hold the balance once you stop moving forward - your sliding foot has to compensate for everything, and that causes lost of consistency trouble.
Ideally, you can "place" the sliding foot just under your body's CG in the monet you let the ball go - which is, with good timing, just before the ball passes your ankle. In this position the upper body's CG is just above the standing sliding foot, and the rest of the movement is balanced through the trailing leg as well as the stretched arm.
Timing is everything, and a good body posture, keep the body tension up until the ball actually moves across your target on the lane.
--------------------
DizzyFugu - Reporting from Germany
Confused by bowling?
Check out BR.com's vault of wisdom: the unofficial FAQ section