Ok, so I used the 1/8" Aluminium settings by @SWomack found at RazorWeld Tool Set for SheetCam - #12 by SWomack once I got them imported.
This was the result:
It also seems to eventually just give up and sit higher than the 3.81mm pierce height in the settings, and cuts way higher than the 1.524mm that came in that file.
Though I tested the 16 Gauge Mild Steel setup on some 1.6mm steel I have (Close enough), and it cut the same thing absolutely perfectly using the 16 gauge settings from that cutout.
So at least I have this file in some 1.6mm steel I guess. Would have looked nice in the check plate.
My thought is that it just gives up with the check plate and just doesn’t like it.
I’m going to run into town to do some errands, so I will check in on this thread when I get back in about 2 hours, I’m not ignoring anyone’s help, and then I’ll probably catch up on some housework, and then get a chance to play with it. So maybe 4 hours at a conservative guess.