I think it is not as tricky as it seems depending on your ribcage. I was pumping with Small ones and then tried moving up to the L ones, but it was a totally bad idea. For some reason, when the contoured ones came out, a light appeared in my head and I ordered them. So I kinda jumped from Small to Contoured Large. And I feel like I am never going to fill them, haha ;D I have a tiny tiny ribcage of 25'', so it is definetely not a problem of rib size, maybe it is more related to how your breasts are positioned in your ribcage and such. I'd go for the CL, they made my life quite easier, but I have to swirl them until I find the perfect position.
You are having a great progress, go with your guts. Try to think what made noogling difficult for you at first, for me, it was definitely the flat aspect of the domes.