Example 5, version 1

[mikemeister_admin]

I used the threshold method on this version & preferred RGB over Lab.

[-default]

Nice - what I like about this version is that you did not overdo it and lose detail in the lighter areas of the image.  Another area to think about is the amount of detail in the darkest areas.

[mikemeister_admin]

I think that because the original image was underexposed I may have lost some of the detail in the darker areas.  Of course, when I have a better understanding of curves, perhaps I can recover some of that detail!

[-default]

Yes, there is a move called a "lizard tail" that may be useful for this image.  It's a sharp steep bend at the extreme end of the curve that adds highlight or shadow detail.  The main thing to look out for is noise in the shadows.