[Yoda]

I find it difficult to understand the drawings in chapter 2-C-4-A.

That's a reverse loft putter making impact on center, above center, and below center, respectively, right? The on center impact is said to produce no spin, the above center impact overspin, and the below center impact backspin.

Why did Homer choose a reverse loft putter for this drawing although it is almost impossible to find any reverse loft putters on the market?

For a regular (positive loft) putter to make above center impact like the one shown in the middle picture, should the putter shaft lean forward (to compensate for the positive putter loft)? Would that require that the ball be placed further back in the stance?

The bottom picture shows an impact below center with a backwards leaning shaft. So impact in the bottom picture must be past low point when the putter head is already rising again. Why would that not produce overspin?

Par71, taking your questions in the order asked:

1. Why did Homer choose a reverse loft putter for this drawing although it is almost impossible to find any reverse loft putters on the market?

ln the Ideal Application (Horizontal Hinge Action / 2-C-1), Impact is illustrated at Low Point. In this theoretical application, the golfer's left wrist becomes Flat and Vertical at Low Point. In actual practice, it normally becomes Flat and Vertical at an Impact somewhat prior to Low Point (7-10).

In Sketch 2-C-4-A, Homer is illustrating three different Impact Hand Locations and their subsequent effects on the Line of Compression. As you have noted, he is also illustrating a reverse loft putter, but that is only incidental; it is not the primary point.

To your question though, there is a definite reason why he said elsewhere (6-B-3-0) that Swingers can use such a putter to produce Overspin. Indeed, true Swingers must use a reverse loft putter. That's because, in a true Swing procedure, Centrifugal Force -- and not the golfer! -- aligns the Clubface for Impact. In so doing, it preserves the built-in Loft of the Club.

Assuming a geometrically-correct Impact, a club with loft can only strike below the equator of the ball. This will produce Backspin. Similarly, a club with zero loft can only strike the ball on its equator. This will produce No Spin (or 'skid'). Only with a reverse loft putter can the Clubface strike the ball above the equator. This -- and only this -- will produce Overspin.

Of course, Hitters and Manipulated Hands Swingers do not rely on Centrifugal Force to align the Clubface. Thus, they are able to produce a 'negative' effective loft via a more forward Hand Location at Impact, thus rendering a negative loft putter unnecessary.

2. For a regular (positive loft) putter to make above center impact like the one shown in the middle picture, should the putter shaft lean forward (to compensate for the positive putter loft)?

Yes. See my last two sentences above.

3.Would that require that the ball be placed further back in the stance?

No, but it would help.

4. The bottom picture shows an impact below center with a backwards leaning shaft. So impact in the bottom picture must be past low point when the putter head is already rising again. Why would that not produce overspin?

This diagram illustrates the common misconception you have stated; namely, that "hitting up" will produce Overspin (2-J-2). Impact below center will always produce Backspin. Again, only when Impact is above the ball's center can there be a true Overspin.