I saw this thread just by random chance and quickly joined up as I have two very large dual line kites.
I have one of the original Force 10 wings which is 15 feet by 5.5 feet.
Mine is the non-Carbon frame version so it's kind of heavy but flies surprisingly well.
That kite flies on 150 feet of 500 pound spectra line.
Funny story: I bought the Force 10 from Windborne kites and apparently the original owner bought it, flew it exactly once and was terrified of it
and returned it so I was able to purchase a mostly new Force 10 at reduced cost and I've had it since 1991.
I also have a GBK by Colossal Kiteworks formerly of Gwinn Michigan which produced a kite that is 19.5 feet by 10 feet.
That kite flies on 250 feet of 3/8" braided nylon rope and has an Easton Aluminum/Carbon articulated frame.
My Force 10 wing is close to two decades old now and still flies although I do so sparingly. Here's a cellphone pic the last time I flew her:
To get a feel for the size here's a picture of it assembled in my living room in front of my couch, it dwarfs it:
The GBK is enormous in comparison - it's so big I can't assemble it in the house really.
I have a still shot of me flying it in Port Aransas, Texas way back in 2003 here:
It doesn't really give you a good idea of how big it is: it's 250 feet up and that day I had a 100+ foot tail on it just because. A man and his daughter saw it from several miles away and walked for over an hour to get close enough to see me fly it close up.
I really need to assemble these and take good clear color photos since they are old now and the kites have probably seen better days.
Just wanted to update the thread a bit!