i wasn't aware the 5.5 came with a carbon mast...

http://www.buttesailingclub.info/events_2006/Almanor%20CampAndSail%2006/Almanor06119.jpg

if the mast is not the original then he should try to find out who made it and for what boat

if it is a nacra mast for the f17? then he could start by looking for tuning information for that boat

http://www.f17class.com/pix/1391605675_749e3db0bd.jpg

where does he sail so the expert mast tuners can chime in if he's nearby