My stoma is approz 3/4+. The company that I deal with is Holister. I had problems with placement and one style (flat and precut). I found one with a concave configure which is adhering really nicely. I try to line up the valve between my pubic area and the leg making a mark on the pouch to match same mark on my skin. That way it ends up where I want it.
I used the 2 pc deal only a few times then went to cutting the opening myself and now I use the one piece and it is great inspite of everything before hand.
If you need numbers for your own research, em me.