Having trouble with torch heigth

[bad-rat-57]

Still dry running my machine. Having trouble getting the torch to go to the correct cutting heigth. I have a sliding z mount. On startup of program, torch goes down, touches material, zero's itself and goes back up to 2"travel heigth. Goes to work, lowers to plunge depth, transitions to cut depth, but goes too far. Torch head is sitting on material and sliding z is about .2" from its stop - so torch is .2" too deep.

Here is a bit of a program I was using as a test when I was observing this.

G0 Z2.0
X8.4762 Y4.3641
Z0.25
G28.1 Z0.12
G92 Z0.0
G00 Z0.00
G92 Z0.0
G00 X8.4762 Y4.3641 Z0.25
M03
G04 P0.25
G01 F120
X7.9968 Y5.2417 Z0.625 F100
G03 X7.9968 Y5.2417 I-2.7551 J0.0000
M03
G0 Z2.00

The settings are just arbitrary settings for plunge and cut depth.

The settings in Mach3 are switch travel - 0.2", pierce height - 0.25" initial cut height - 0.63"

The settings in sheetcam for the drawing are pierce heigth - .25", cut heigth 0.625"

Any thoughts what my trouble might be ?