from my experiance , estimating dose from different vendors is bad gamble
Many vendors are not even sure of their exact species and sub species , or if they are even active
also how their are grown plays a major factor in strenth , Their not susposto be watered for the last 6-12 months for maxium potency , Most vendors will water them before harvest for extra weight
If your into 'it' you could buy from several different vendors live logs or end cuts , grow a piece and do the rest labeling each specimn with a approx potency