Back to KC's original query. Part of the advantage of the tapered mast is not only less weight aloft, but it is also added flexibility. The tapered mast is more flexible aloft, and when a puff hits the boat the mast bends more and gives more "shock" absorption. That is part of the reason the DS removed the jumper stays from the top of the mast.
IMHO drilling holes aloft would weaken the structure of the mast, and possibly cause it to buckle. But I really don't know. I haven't tried it.
I really think there is an advantage to the tapered mast. I was the only non-tapered mast at the DS North American Championships last week, in Annapolis, and I'd like to think it was at least part of the reason I finished in the bottom third of the fleet.

J .P. Clowes
Eastern Great Lakes Regional V.P.
DSI 14083