It seems you have more upper body than legs. The good thing is that this will provide you with a low center of gravity which is good for aikido
Also since your weight indicates you are a bit round I would suggest going up a size rather than down. You would be happy about the extra width, and the extra length also come in handy if you have a long upper body. It looks really silly if the lapels under the belt are short.
I am roughly 190 lbs and 182 cm tall. I use a size 5 from Tozando. Fit's perfectly... however NEVER ever wash it warm or tumble dry it. It will shrink in both length and - depending on how it's weaved and sown - width.
I don't know what they will allow for you in your dojo, but I have a few karate gi's that I enjoy during summer. They are cooler, and they fit better around the waist.
But first and foremost: ask your sensei or your club mates. They will be able to help you.
Seek out someone of the same height and girth if possible, and ask what they use.