i believe body weight does have an effect
i have 2 friends that are severly obese, im sure most americans know someone like this, there about the same size peter from family would be in real life, there really big, maybe up to 350-400 pounds
for their first time, one of them took 2 really dense milkshots, and the other took 3 small bong rips, neither of them got considerably high for the amount they smoked. if that was me my first time, it woulda knocked me on my ass
i remember hitting a tiny acrylic bong in my early smoking days, nothing even comparable to the glass on glass diffused ice notched bong my fat friends were hitting, and i took a bitch hit and coughed it out and still tripped out
and has anyone ever smoked out a kid below the age of 15 whos small and thin, ive only done it 3 times because every times the kids swear theyve been killing half ounces of "purple kush" every other day, but when it comes to them taking a toke of kush with me, they all tripped out after the smoke made contact with their lungs, even though the tokes were so small you woulda swore they havent smoked anything in their lives
so yes, i believe that body size does effect how high someone gets,