i've been trying for so long to scale my ui elements such that they are the right size and actually in frame, but it's so hard because idk what the pixels are in relation to
does it start from the top left?
how big is each pixel relative to the mfd?
Since the coordinates on an mfd of one by one meter go from -100 to 100 (so 201 pixels in total) each pixel should be around 0.5cm (At least if you don't tinker the resolution).
The "start" (0, 0) is in the middle of the mfd, the right border has the same x value as the width of the mfd (in centimeters), the top border has the same y value as the height, bottom and left border have the same values, just negative.
Also, in case you don't know, you can get (and maybe even set some, I've never tried that) the properties of the mfd screen itself. Just use the normal blocks (e.g. get widget size) and use
_Screenas the widget name. That can be useful for making programs fit different screens.