I assumed you were talking about the way the helmet looks a bit like a yamulka, like it doesn't come down far enough on the sides and back. (the gap between your ears and the helmet) That's why I thought of the Nutcase, because they are deeper top-to-bottom and might cover more of your skull.
If you are talking about oblong front-to-back problem, like you have an aerodynamic skull; I've had good luck with Bell Citi and most Bell helmets. Giros are far too round for me, crushing my forehead while leaving wide gaps on the sides.
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