The luff lenght on the 5.7 is 431cm so all you need is a 45cm extension. Aeron and chinook do one that does conventional masts as well as skinnys, just make sure you get one with pin that goes right through the ext and not the one with the two locating pins. If you can afford the $ I highly recommend a skinny. You could also get a dedicated skinny ext that goes pass 31cm
www.severne.com/ Um go to severne.com if you like trees.. Go to
www.severnesails.com if you want to look at sails