I find that Wranglers are cut slimmer than other jeans (e.g., Levis), and the slims work well on my very thin son.  Amazon was the only place that I could find 16S.  One reviewer commented about the odd creases that form down the legs during laundering.  I've also found this to be true, but it hasn't been a dealbreaker.  Although my grandma would have ironed these, I do not!  My son is outgrowing these (in the length) so I'm sure hoping they have 18S available next fall!