Get the lightest mast you can afford! Holding the mast on land does not give you a good idea of the difference in weight that using it on the water will provide. It isn't just the heft of the thing as you raise the sail with the mast in it, but it is so much more and it's dynamic. 75% will serve you well, and will be much much nicer than a 30-45%, and will make sailing your gear that much more enjoyable. Get a good mast to begin with and you'll be spending your hard-earned cash well.
(Note: I don't sell anything, but I sail a lot of things and have learned over time to try to do it right the first time.)
cheers (but we are having rather English weather here in New England...)