I also created some 4dKH water for my CO2 drop checker using a very accurate sub-gram scale and baking soda. I had gotten pretty close with a Taylor scale that I use for ultralight camping, but this scale is much more sensitive for small amounts in the tenths of grams. I purchased a calibration 100g weight, and it was 99.98 percent accurate without calibration. I'll also be using this scale when making up GH booster solution going forward.
I am pretty excited to hear there is another aquarium hobbyist that is into ultralight backpacking/camping! Ultralight backpacking is my first passion with aquariums being my second. I find that both tend to cost more than ever originally planned.