medium or large swaddlebees??

ok,ive been dithering over these for a while, i had 1 when emilie was small& loved it and want to get another 1 to try now - swaddlebees ocv pocket, just cant make up my mind if i need a large or medium?
shes 9 mths, 19.5 lbs, 15 " waist & 10"thighs, so in theory could probably wear either, but then if she gets skinnier when she starts wakling will a large fall off her? and ineed a highish rise!
aaargh, decisions!!!
somebody make my mind up for me

Summer is 15lb and about 65cm her mediums fit her on the tightest setting if thats any help

thanks for that, whats the rise like on them? em's 74cm.
im thinking the med would prob be ok as long as they dont give a builders bum.

The rise isn't that high ...

ahhh, shes cute!!!!!!!!!!
hmm, think i might go for the mediums, em looks a similar build to summer & got a feeling the large wont be tight enough round the waist - got a large itti bitti & on tightest settings is slill slightly too big at the back.
thanks for the help!