well let me put it this way.....do you care about how big your arms are or how big they look? me i care about how big the look. and i would say that doesnt have much to do with weight.
1" per 10 pounds? i think that is a pretty shitty generalization. say you start out at 170 which a lot of guys do with 14" arms. so when you get to 240 you will have 21 inch arms? sure didnt work for me that way.