In my experience it is better to measure the number of shrooms you are taking as the max. dose per shroom is pretty consistent vs. measuring the total weight.
If only Psilocybin was available as a substance so we could just measure μg directly.
When you buy dried shrooms, it's not easy to tell what one fruit is because they shrivel up and break easily. Some sellers break them up deliberately - if some fruits are more potent than others, then by mixing them, the total psilocybin content is more likely to be similar in every package they sell.
Interestingly, some vendors sell "mushroom pills" and "mushroom chocolate bars," where they do this on a bigger scale - mill the mushrooms down into powder form and then thoroughly mix the powder to give an even distribution. The idea then is that each piece of chocolate in the bar contains the same amount of psilocybin - and with some trial and error taste testing, they can recommend how many pieces of chocolate to have for the desired effect. This also doesn't give you the same nausea you typically get by eating the dried mushrooms directly, which might give you a better trip.
If only Psilocybin was available as a substance so we could just measure μg directly.