I was reading on the binder I want and their size chart is as follows...
•XS:bust:72-80cm=28.35-31.50inch under bust:60-68cm= 23.62-26.77inch weight:40-47kg=88.18-103.62pound
S:bust:80-87cm=31.50-34.25inch under bust:68-75cm= 26.77-29.53inch weight:47-55kg=103.62-121.25pound
•M:bust:87-94cm=34.25-37.01inch under bust:75-82cm= 29.53-32.28inch weight:55-62kg=121.25-136.69pound
L:bust:94-99cm=37.01-38.98inch under bust:82-88cm= 32.28-34.65inch weight:62-70kg=136.69-154.32pound
•XL:bust:99-106cm=38.98-41.73inch under bust:88-93cm= 34.65-36.61inch weight:70-77kg=154.32-169.76pound
XXL:bust:106-113cm=41.73-44.49inch under bust:93-99cm= 36.61-38.98inch weight:78-85kg=171.96-187.39pound
Right, so my worry is that I won't get enough flattening seeing as my chesticles already flatten pretty well with a sports bra, BUT I definitely don't want to go too small and restrict breathing.
I haven't measure very recently, but know I am 34-36 in. underbust, and only like an A cup or less.
Advice?