I wondered that exact same thing Shane:) I even ordered some photopaper from Amazon, but then couldn’t wait and just got stuck in. I did worry a little about measuring the results though - since gripping a solid piece with the verniers is easier to measure than lines on paper.
I also wondered about getting a laser cut mask with 0.2mm lines 120mm apart and using modified laser_spot_test.form files in conjunction with photodiodes hooked up to a voltmeter to measure when the laser spot was brightest through the mask.
But the laser spot test file seems to slow the galvos down universally - both when the laser is on and when it’s off - so it takes 18 minutes plus for the laser spot to appear at the side of the build platform as the galvo slowly tracks across from the middle. Which was only a little faster than printing the calibration pieces, plus the effort of getting the mask cut and wiring the diodes. I did buy the photodiodes though - oh well, they’re on the shelf with the photo-paper 