All main dimensions are strong withheld according to prototypes. Some secondary sizes can have the minimum divergences which in a game can't be caught. These sizes have no slightest effect on the general visual perception, or, about any concrete size wasn't succeeded to find exact data. For these reasons of special attention to them it wasn't given. Other words, approximately, intuitively.
Similarly with forms. Actually, about correct (or wrong) forms you can judge by real photos.
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