The statement that the Trichocereus Peruvianus is 8-10 times stronger than the Trichocereaus Pachanoi is based on one investigation and can probably really not be trusted. Its strange that there is so little investigation done on these cacti and their mescaline concentrations. This also is true for the identification of different species in the Tricho(cereus) family.
The fact is that for all species of the Trichoreus and the Cereus for that matter, is that the concentration of mescaline depends completely on the conditions the plant was grown in. The amount of sun, water and soil compensition are all important on how the cacti will develop. I think the concentrations in cacti grown in Holland for instance are much lower than these grown in South America, I was always told that the amount needed for such a cacti is about 800-1000 gram for fresh cacti , this is the complete cacti then.