I don't see the point of sizing up on thin finns, if you want a looser fit, just get slim jims. Those thin finns that guy posted obviously look bad. I'm sure most of you have a store around you that sells nudies, all this wasted time asking about sizing up or sizing down can be easily avoided by going to a store and trying them on for yourself.
But my honest word of advice is to size down to the smallest size you can possibly get on because they will stretch. But I do like my jeans to be fairly slim fitting.
i'd say size down on everything except slim kims. i went down to a 28 on mine and have had 'em for about 2 months, can't really say that the waist stretched out haha.