turns out either the original design is inaccurate or the freecad STEP import didn't work well: the rpi mounting screw holes were off but some sub millimeter length: 58.2x49.05 vs 58x49 actual. see rpi drawings in https://datasheets.raspberrypi.com/rpi4/raspberry-pi-4-mechanical-drawing.pdf
this also means the STEP file is replaced with a freecad native file format. the master sketch comes in very handy when designing mount and other constructions around the LCD.
