San Pedro cactus Powder dose - help?

[meep]

Sorry Swiy's - swim need help with his maths.

Swim has 900g Powdered san pedro, he is planning to trip with 4 friends.

Swim has read that 100g dried = 300mg Mescaline (3%)
Other sources say its more likely 100g dried = 200mg Mescaline (2%). Assuming that Swim cactus is average hes planning (hopes for) for a 2% containing cactus.

Based on this math and the erowid guide of Light = 100 - 200mg, common = 200 - 300mg and strong = 300 - 500mg Swim is planning to choke down 175g of powder aiming for a 400mg (strong) trip.

Because swims cactus is coming already powed he is unsure if the math changes. Swims logic says 100g feather is the same weight as 100g lead so 175g powder is the same as 175g of dried chips? Please help swim with this, he knows this is silly but he is worried about having a massive dose by accident. Swim will only get one go at this in the near future and would rather not have a light trip without breakthrough.
Thanks!