Well if it's not the correct wieght are you gonna get your money back, my guess is no.
Secondally get scales if you are going to be getting fairly chunky bags of grass. Use the search function their was a few pics of 1/2 oz a few days ago in this forum. Just another point all weed has different desities, i've sold poeple 3.5g 1/8 bags of really compact weed and they think they're being bumped until I wiegh it out infront of them.