FWIW, since you apparently haven't played neogeo games, either at all, or not very often, they only use four buttons. Like me, it won't matter how they're situated, since I never played them in the arcades. NeoGeos aren't just fighters and such. Isn't Metal Slug a NeoGeo?
Also, your orientation for 3 and 4? You could go with a square set at a 45 degree angle (diamond.) While I haven't been able to play it yet (setting up software currently,) preliminarily, it feels good. Since the middle finger is a bit longer, it hits the top button, while the index and ring fingers touch the buttons on its lower sides. AFAIK, only a few select games actually use the 4th button for P3 and P4. (From what I've heard, mainly the D&D games, I think, something in that genre.) Someone confirm.