I'm getting some t-shirts hemmed as they're always too long. I googled quickly and standard seems to be halfway down the zipper or at about jeans pocket height. Is this correct? I guess it will be different depending on your own proportions. If this is standard, I'll probably eyeball it +/- 1 cm to what looks best. Also, I washed and dried them once. Should this be enough? Will they significantly shrink with repeated washings? Thanks.