Bob...For what it's worth, my Moon mandolin has a mahogany neck with a rosewood fingerboard and no trussrod. When I asked Jim Moon about this he replied that he didn't think a rod was required and might actually weaken the neck at that angle be removing too much wood. I think I agree. At any rate, it doesn't suffer from having no rod. I figure a maple neck (I intend to use an ebony fingerboard) needs a truss even less.

Peace, Mooh.