Pro Furling System CC 37
I wouldn''t think concern for chafing on the lifelines, rails, or stancions should mandate drum height, it''s just a fact of life to live with, with perhaps an exception if you are voyaging around the world where chafe deserves such concern.
As to the height of the drum, IMHO make as low as possible to max the luff length. Consider room for the anchor if you carry one in a bow roller. Have a sailmaker measure/calculate the new luff length, cutting down a sail is expensive and you don''t want to get it wrong (whci i can tell you is easy to do...)