[bignose]

While I think that Pelz does have a fair amount of good information, the 17" inch rule is just silly. Pelz himself actually knew that at first -- one of his very first articles back in the '70s talks about how the optimal distance past the hole varies from 6" to 24", depending on the current conditions. I.e. how fast the green is, the slope the hole is cut on, etc.

You can't actually talk about distance beyond the hole, you have to talk about the speed at which the ball arrives at the hole. Specifically, you want the speed to be such that gravity has enough time to pull more than half the ball below the lip of the hole before the ball hits the back wall.

And, there are a lot of factors to consider -- the slower the ball's velocity, the wider the effective width of the cup is. I.e. if the ball is tracking at the very dead center of the cup, it can be rolling as fast a 8 revolutions per second (rps). But it has to be dead center, because at that speed, the ball needs the entire 4 1/4 inches of the cup for gravity to pull at least half the ball below the lip before it hits the back of the cup. In this case, the effective width of the cup is about the width of one dimple of the ball -- because if the ball is to the right or left of center by more than one dimple width there is practically no chance the ball will fall in the cup.

If the ball is moving slower, 7 rps, the effective width is greater, about one quarter inch to either side of the center line. 6 rps = a target one inch wide. 5 rps = a target 1.5 inches wide. 4 rps = a target 2 inches wide. 3 rps = a target 2.5 inches wide. 2 rps = a target 3 inches wide. 1 rps = a target 3.5 inches wide. And, of course, the limit of 0+ (a teeny tiny bit more than 0) the target is the full 4.25 inches wide.

There are three competing considerations: 1) the need to reach the hole, 2) the need to preserve a wide target and 3) the need to minimize the comeback length

The first consideration obviously likes higher speeds, and the last 2 obviously like slower speeds. 2 to 3 ball revolutions per second seem to be about the best compromise between all the considerations.

And at a speed of 2 to 3 ball revolutions per second at the hole, how far the ball rolls past the hole is completely and totally a function of that day's green speed and conditions. There is no one-size-fits-all distance past the cup that is perfect.

It is a catchy number, and it is easier to know that ball went 17 inches past the hole than it passed the hole going 2 1/2 revolutions per second, but nevertheless, it isn't right in every single case.

p.s. to give credit where credit is due, most of that analysis is in Geoff Mangum's book Optimal Putting -- which I highly recommend.