The house style we're working in stipulates en dashes with spaces on either side rather than the longer em without spacing. It's uncommon in the US (and it's a US publisher) but it's their house style, and one of just a few minor deviations from Chicago Manual of Style. However, Calluna Sans's en dash seems so unusually short as to nearly be mistaken for a hyphen. My initial response is that it looks atrocious as stubby substitute for an em, with rivers of space on either side, comparatively. Perhaps Calluna's en was never intended for the styles common in Germany, the UK, etc., that don't favor an em for parenthetical thoughts. Would it be justified and legitimate to customize the en by lengthening it slightly, or is this typographic crime, and how would such a basic customization best be done?