Hey Jeff,
IMHO, for the average tweener, the true concept of skid flip is very difficult to execute, let alone comprehend. What I mean is that if you drill a ball that can literally hook like Robert Smith's ball in the backend, your average tweener will never be able to use it because he/she won't understand the true angle it takes to throw that ball. That's why some balls that end up being skid/flip are labeled as O/U because we simply can't throw them accordingly. This is why the strongest motion we tend to like is the strong arc as Bob has mentioned and usually that is enough.
There are always exceptions of course because I saw one show where Randy was talking about the ball reaching 48-50 ft before it made it's change of direction...? Not me bud, I can't even see that far, let alone trust a ball to react from there...
