Your saber must be different because mine is only hollow to the choke point below the grips. There are then two seperate pieces that go over the main one.
So as I see it on mine it would be a long narrow resonation chamber. Definately around or less than 3/4" and the length of the pommel.
So much work... where are you thinking of putting the Aux button? My only thoughts would be the brass bike valve up top. Thread it onto a momentary. Or maybe it's a crack dream but in one off the three allen heads/LED holders up top.
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