Wow. Lot's of good comments here. Especially regarding the swing plane for someone that may have an 'obstruction' that prevents them from a linear swing plane.

In your original post, the problem you described is one of release. From what I have witnessed, there is alot to be said about the bowler-to-ball-weight ratio. The larger bowlers seem to whip the ball around like it ways 8 pounds instead of 15-16. (They also don't need to swing the balance leg to the opposite side because the ball just isn't going to pull a larger person over as easily as a smaller-framed person.)

So...the release...launching the ball is usually due to:

A ball fit issue
Ball is too light
Ball fits, but the bowler is squeezing it
very early timing

I hope this helps...