Just arrived, I ordered the size 18. I', 5'9" and 170 pounds. The fit is perfect but the legs and sleeves are a few inches longer than I expected them to be. I am wondering if a 16 would eliminate the length problem since my height is in the size 16 category. On the other hand would it fit to snug since the 16 has a lower weight limit. To bad they don't make a 17. BTW, for anybody who does order these, your diaper will be very visible.... which is awesome. With regards to the zipper I was able to get it all the way up fairly easily and secured with the help of a mirror. It took me almost twenty minutes to get the zipper back undone. (And im pretty limber) Highly recommended to have a partner to help you since if you cant get it, your pretty stuck in your PJs.