Maybe also try a front zip if you are shopping for one and/or your instructor has those for rent. When I was fitting clients for rentals at the shop where I was a DM, ladies with more generous curves often found donning a front zip to be less awkward. Once you get the arms on, you can hunch your shoulders to create some slack around the front zipper. You can also just leave that zipper partially undone until you get wet. The water will give the suit some more give.
I am pretty curvy and I dive the Bare Evoke (a back zip). Definitely stretchy and not only is it built a little curvy to start with, but on my 5mm, it also has a short “comfort” zip at the front of the neck. I leave that undone to add a little more give in the chest area until I’ve started the dive. If I am cold or there is a lot of water flowing in, I just zip it up.
One last suggestion on the wetsuit front is to think about layering a vest or other top under the wetsuit. It would allow you to use a thinner overall suit and add warmth to your core. I have a sharkskin chillproof top that is made of a wind resistant fleece and adds the equivalent of 2-3mm of warmth without a lot of bulk. I can put that on and add a 3mm full suit over it and 3mm suits are going to be much stretchier than 5mm. Besides Sharkskin, there is lavacore, thermoprine, and bare just started making a line called Exoware that I think is similar. I don’t know how the other brands fit, but my sharkskin is cut pretty generously in the chest area. I actually had to go down a couple of sizes to get it to fit snugly enough.
Related, if you are looking for a BCD that accommodates a curvy chest, take a look at the Oceanic Hera. The shoulder straps are on a sliding rail that allows you to position them forward towards where the waist cummerbund is or tucked back under your arms. I wear them tucked back so they aren’t pressing on my chest. Though this being scuba board, I anticipate a horde of zealots to rush in and tell me I should just recommend a backplate/wing anyway.
Good luck!
