Just maintain the same "overall weight" of the catamaran but delete all reference to the mast weight and/or structure (other than it has to be a "mast" and not a "wing") then any reduction in mast weight and/or structure would be relatively minimal to any difference in performance whether real or just percieved. Carbon fibre for masts will very soon be a necessity for most sailing craft, not primarily as the means of obtaining "better performances" but as the means of securing actual supply of masts, and by not incorporating that realisation NOW will not only create greater problems in the near future for the supply of masts but it will also tend to "restrict" future growth of the class.
Beides, if anyone has a problem with something as "minor" to overall performance as the variation in the small difference that "mast tip" weight will have over the individual sailing skills of the relative sailors, then give the aluminium masted boats a small percentage handicap advantage,
(like 0.0001% should cover it)