buy a digital scale and make him throw it on there in front of you,if he ask "what,don't you trust me?" a blank face,a stare and a firm "No" will put him in his place,it makes me sad that fellow stoners can't just stop being greedy,it's called self control and they should learn it,if i'm sold a skimp sack i'd tell them to pay me a few bucks to make up for it or would ask for him to add some to the next sack to make up for it or would never speak to them again...but if it where my brother i just would'nt buy from them again if he refused either option,like you said,don't wish to alienate a family member.i used to get skimp sacks all the time,i got sick of it and now demand to see it on a scale(digital only,hang scales are inacurate)or tell them they can keep it