MESA THCAD-2 - couple quick questions

Hello and thanks for being so awesome. Hope you all had a merry Christmas.

I'm building a CNC plasma based on the LowRider v3 motion control system, guided by a previous build by Kyle (@kd2018 at the V1E forum) which was based on the LowRider v2 motion control system.
 
Kyle had shared an immensely helpful wiring diagram image, which I have copied and tweaked to match my specifics (somewhat).

Where Kyle used MESA THCAD-10 ... mine is THCAD-2. His diagram calls for grounding ("to star ground") from the analog ARC input area of the THCAD-10. See below. However, according to the manual for THCAD-2, the two center connections (other than + and -) are "unused" — do I need to find some way to ground via somewhere else? Or can I ignore that part?
 
Where Kyle used MESA 7i96 mine is 7i96S. I do not know if this requires any changes. See below. ??

Below are Kyle's original diagram and my tweaked version.

KYLE's diagram:



My Diagram:
 

From the docs, it looks like the THCAD-10 had integrated resistors, and is doing the voltage dividing on-board, which given the voltages (and likely noise) probably needs a strong power-ground plane to keep noise out of the rest of the circuit. The THCAD-2 requires an external resistor and probably assumes that the HIGH voltage electrical noise will be far enough away from the rest of the board to not need it.

The board has a ground *reference* through the signal ground to the rest of the system, so I'd assume you're ok without wiring to "star" ground.
If you're worried, you can look at the traces from those two center terminals that would have been to ground on the *-10 part, and see what the connect to, and use that to make an informed decision. Generally, though, if the designer says they're unused, they mean it.

I'm new here, btw, so take this with a grain of salt. Maybe PCW will chime in with an authoritative answer.

+1 for Tommy.
Initially, I grounded the THCAD HV side but found due to a  mains bond from neutral to ground in the building switchboard was part of our standard wiring in .AU. I found that this introduced a 50 Hz ripple in the torch voltage (from the mains ground) so I don't do it anymore either.

Thank you so much

Thank you, I appreciate it!

Got it. Thank you!

In the somewhat related 2nd question, are there any significant differences between the MESA 7i96 and 7i96S? That would affect the wiring scheme?

The THCAD2 does not need a input side ground.
(the + input is the analog input reference/ground)

The 7I96S wiring should be identical to the 7I96 with one exception:
It's better to use output 4 or 5 for plasma connections as they have better
isolation and will couple less plasma noise into the rest of the system.

(as long as the 100 mA output current limitation of outputs 4/5 is not an issue)

@PCW

Thank you! So, based on my screen shot below, am I understanding you correctly on what change needs made?

Yes