The "3,4,5" in the chemical name of mescaline (3,4,5, trimethoxy-PEA) has to do with the position of the methoxy groups on the benzene ring, it has nothing to do with strength. Peyote and San pedro have the same ingridient (mescaline) though there is debate about the presence of trace amounts of mescaline analogues that add a certain "flavor" to the experience.

And Pumert you should use about 12in of San Pedro for a good dose, 18in for an awesome dose.