I've been using similar for a while. The only problem with these kind of scales is their height. the VTF of the stylus really needs to measured at the same height (or close to) as it sits on a record. Measuring it at the height of the scale will result in an undermeasurement.
To get round this, fashion a small platform from an old credit type card , by bending it in two places (I used a hot knife) a little less far apart than the height of the the platform and stick one end to the platform on the scales. When measuring place the stylus on the overhanging platform formed by the card, which should now just hover a little over the platters surface. (also gets over the magnetic issue)
I've tried it on an Ortofon MC tracking at 2.3g. It measures correctly using the mod, verified using another scale, but measures over 3g at the scales platform height.
I can post some pics if you like.
With mod to scale:
These particular scales are non magnetic, so the difference is in the height above the platter that the measurement is taken (true the mod itself could flex, but measurement with a Shure scale suggests not).
Hope this helps.