Having recently checked the calibration of five (5) VP2 (0.2mm) tipping spoon modules (3 from one order and 2 from another) I would have to say these 5 units are very consistent and actually within stated specification of +/-4% with most reading a tad under, average of the 5 (each was checked twice) was 100.5% Standard Dev 3.2%. One would not be expecting any better than that and even thinking of trying to calibrate these any further would not even be a consideration let alone be able to be done properly.
The original VP2 tipping buckets were typically not even close, out of the box could be up to 20+% in error and generally always under reading.
However the VP2 tipping buckets could be easily adjusted, these tipping spoons have no real practical calibration means what so ever and yes I know how the calibration works but there is absolutely nothing practical in calibration terms with these tipping spoons. The non linear nature and having to remove and dissemble/reassemble really makes any form of field in-situ calibration not an option.