Maximum's probe depth below the deck

What is the maximum cutting reach below the base plate, I need to cut a slot into a 200 Lb c-channel that want fit on the cutting stand. A quick response would be helpful I’m going to find out in about a hour.

Depends on how your Z axis base plate is mounted and your torch and its mounting position.
Z has about 2” of travel. Whether you can successfully probe the work surface at the extreme is another question. Not much push from the spring at that point.

Why aren’t you cutting from the flat side instead of from inside the channel?

I am, sitting on my table its to big and arcdroid is on a fixed base (my bad build two will be much better) I’ll figure it out than let you know. By the way I’m building a straight line cutter for sheet steel put my old cutter to work