I've been binding via a diy method for nearly 2 years now because i could never afford a binder, but i finally have saved up just enough to get one, but i have no room for a mistake when it comes to buying a binder as i wont be able to buy another one if i mess up. So heres the thing, i measured my chest like it said on the underworks website, and results were that my average chets size is 30.5, basically thats between the small and the extra small. I really don't know which one would benefit me best, i want to get my chest as flat as possible and i also want to be able to feel slightly comfortable at least. I'm just not sure what to do. I am currently losing weight also, so i'm not sure if i should just go for the extra small. The model i am looking to buy is the tri-top 983. It will cost me £30 ($50) including shipping to get it to the uk which is alot of money for someone with no job/income. So i have no room for mistakes. If anyone could give me some advice on what size to get or what to do i would apppreciate it alot.
Thanks

You're only 1/2 an inch smaller than my suggested size was and I also ordered the Tri-Top 983.  I got a Small - and it's done really well, although it's time to get another because it's getting a bit worn.  But I would suggest that you go for the small - and they're a lot tighter fit than you think.  I know how expensive they can be with shipping as I live in Australia, but they're not so expensive that getting another one is impossible.  I'd suggest going for the small right now - if you lose weight later on to the extent that you need a smaller one, then you can get a smaller one.  Just my two cents. 

I agree on going with whatever size you are closest to. I got the tri-top as well in a medium when I was closer to a large thinking if I went one size smaller it would be better and it didn't work out well. I got it almost a year ago and only a few months ago it had stretched enough for me to get it on without help. Also I suggest looking up underworks coupon in a search engine because you can usually find a coupon that will at least help lower the price a little.