I'd say for the finger sizes, go a few smaller, because that way you can make them bigger if you need, as opposed to adding tape or plugging and redrilling to go smaller. For span, I think you would probably go from cut of the thumb, to middle of the fingergrip. HOWEVER, if you use a thumb slug, measure from the inside of that.
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....BRUNSWICK!
¡Viva la nación de Brunswick!
Nothing more to be said.
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