Here's some instructions: Power Kite Forum - Converting a Symphony 2.2 to quad line (Now with Flying Video)
Blimey. Respect Low Winds. Third post in and you're Haaking. What that means is resurrecting a post from long ago. Its named after KiteCrowds most prestigious Haaker. Haak.
Lots and lots of kites have been converted by the manufacturers as kite tec has improved but as you say, there are so many purpose made 4 liners new or on the bay that it makes it almost pointless. Unless its for a bit of fun or a project. I certainly wouldnt advise a trial and error set up on a big kite.
Cock of the year 2012 and 2013 and now 2015.