The 'easy calibration' process is not that difficult and no need to waste the sugar, if equipment is sterile to begin with.
I began with tap water at 20C, then gradually added sugar checking it with an hydrometer (though I found a refractometer easier). I added the sugar in 7 stages of around 0.010 SG per stage, noting the tilt angle at each step. The 0.010 doesn't have to be exact, so long as an hydrometer reading is taken. My biggest problem was finding a small container deep enough and wide enough - all I could find was a 5L brewing bucket FV. The whole process too about an hour.
Once my calibration was done, my sugar water was transferred to my 30L and a batch of red wine started with it.
The 'easy calibration' cannot account for CO2 bubbles collecting on the iSpindel, my experiments with my present wine fermentation, seem to suggest this may not be much of a problem in wine - giving the FV a good shake up to clear the bubbles, the tilt always quickly settles to the same value. Probably more of a problem with beer brewing I would guess, but so variable it would be near impossible to calibrate for.
I was also curious about the need to fix the iSpindel in the PET and how much difference it might make to the calibration. It's a V4 pcb, fitted to a big XL PET, battery soldered and stuck to the pcb with double-sided tape. Mine is a lose, easy sliding fit in the PET. If I shake it, it can rattle, but always seems to land inside the PET in the same position, always floats battery side of the pcb lowest, with my extra weights stuck equally, either side of the battery. It always produces quite similar values when checked before and after charging, if dropped in water.
The further my first batch of wine progresses using the iSpindel, the more impressed I become with it.