That video is from a review,
http://www.extremekites.com.au/reviews/ ... -a-15-r27/
I would guess it's the 15meter
here is another from
http://www.extremekites.com.au/topic/15 ... pe/?page=2
https://www.youtube.com/watch?v=Hm1MxlOuo1Y
Bletti depends on your weight. I have a friend 80kg most used kite with hydrofoil are 8.6 and 11.4 sonics. If you get a 12 it has good over lap with an 18, the 9 you could combine with a 12 or 15. I think the 18 is lacking the performance to race with a hydrofoil, freeride it would be ok. The 9 will be too small for light wind. You wont get more than 2knots ,if that, more lowend from a 15 over a 12. The 12 seems a safe bet.
As to lines you could order both 20 and 22 meter sets and cut one up to make extensions. Otherwise you could email pansh to make you what you want. But the sale could be finished before they reply.... And the lines are half price anyway so it's only $30 and you could make 2 or 3 different extensions out of the 20s. Pity there is no 30 meter option they would be perfect to trim into lines and extensions.
Most high depower foils flag fine on a front line. I am not using a fifth on my A18. I haven't tested the front line flag on it yet but I am sure it will work. I only use a fifth on small kites, there is too much performance hit. But if foils worry you in some way or you want easy/hassle free landing by all means use a fifth. If I was always on snow or land I might use one for some peace of mind.