The overall design is fine. Much props, they are many Sakura cosplayers out there but a lot seem to be off...
As mentioned, the dress is meant to be a bit more fitted around the sleeves & waist.
Like you said, you will need to put the circle in the front as well as in the back, which is slightly smaller than the circle on the front dress flap. The circles on the arms "attach" to the sleeve trim with short trim pieces as well.
Also do not forget about the pouch on the back of the dress on the left side of the but ^^ I'm also guilty of not making the shorts long enough down to the knee too so I am not going to nit pick that!
Some questions though, any images of the collar by any chance? And about the white down the middle, did you just use trim or is that a zipper there? Assuming the zipper since it seems to bunch up like mine did slightly putting it in at such an angle ugh! I use a cotton/spandex mix fabric and I thought it was just because of the fabric I used.
Cons I attend: Magfest, Bootycon, Dragon*Con