you are obviously a very keen sailor so i would advise to save up more money and buy later model small sail.

later model wave sails from my experience are way,way better than earlier models.

i sailed a earlier 2004 4.5m wave sail once in 25knots plus and got overpowered big time.

my 2009 Tushinhgan Rock 3.3m with a 340 or 370 mast is awesome for control in 30 knots.

yes,the 400cm mast will work as sail will have adjustable turbin,smaller 370cm would be lighter and better.

I would rig it on the 4m mast and see how it looks. If it looks ok give it a sail. If it sails ok you don't need a new mast.

Anyone know this guy? The phone number for his ad doesn't work and he isn't answering emails.
www.seabreeze.com.au/Members/Profile/Details.aspx?member=goochy