Here are both the original and new column racks with a ruler for scale. 

  Here is the where the old top maximum height came to when the original stop was in place. I'd already removed the stop and installed the new longer rack when I thought to take this picture, so I just put the head to where it would be stopped by the original setup:

 Here is a side view of the new Z height. I have the top of the head here set flush with the top edge of the column. I can actually go about an inch higher but the head is no longer completely supported at that height. It is so nice to have the extra room! XYZ real estate is precious on these little machines. :-)

 Here you can see how the original lever spring limits how far down the head can go. Even so, with the new longer rack it gets pretty close to the mill table.

 Here is a front view:

 When I get my act together and install the air spring, I'll be sure to take pictures of that process as well. At the time I did this I had a project that was stalled until I could gain the extra Z axis height I needed, and have simply been using the machine this way ever since....!