Hi Travis,
Got any hit on this?
I have a ME-300 that I'm trying to put to work and would love to find some puzzle pieces too.
I was able to make the machine move by using the Generic HP-GL post processor in VCarve and using the checkbox in "Output direct to machine".
I never heard of DNC program before but in short I added a new printer and set the parameters you listed above manually.
I'm sure I can find it if you need the info.
I could only have it to work at one set height though (Z height is set in the controller) because HP-GL only give the command PD and PU to drive the Z axis.
(PD and PU mean Pen Down and Pen Up)
So with PD the machine goes to the set height and goes back up with PU... Let's say it's a bit limiting.
I tried guessing a couple things in the command code to control the Z height but apart from the standard PD and PU nothing worked so far.
I wish I could find information on MGL-iic3 command so I could finish writing the post processor for it!
Every search I did seem to bring me back the numerous Mimaki flyers of their various machines.
Their machines support the command code that no one seem to know about!