We have seen lots of guys posting and asking about what kite to get for light wind and they are dealing with 10 knots. I don't consider 10 knots to be light wind, I don't typically consider 8 knots to be very challenging. It can be if there are lulls but if the wind is steady, 8 knots is a reasonable wind.
I am traveling down to the Caribbean this weekend and it looks like we will have some light wind days. Most days will probably be 8-10 knot days and that is fine. I find that below 7-8 knots, things can get tricky. I think the reason for this is that the energy in the wind is proportional to the square of the wind speed. So 5 squared = 25 and 7 squared = 49, with 5 knots you are dealing with half the wind energy, you would need to double the kite size. Even between 5 and 6 knots there is a very big difference, on the order of 50% more energy with 6 knots vs 5 knots.
I have the Sonic Race 15m, 18m and 21m for light wind and they are also light for travel. I typically use 27m lines with the 21m Sonic Race but could also extend to 33m. I have the Ketos Freeride XL wing and the combo of 21m and XL wing can be amazing. If I can get started and get that kite moving with some apparent wind, I can generally make progress up wind in 5 knots.
I am not very proficient at air gybes and usually do water gybes. Things work well with smaller kites and a downloop on transitions, but I have not mastered downloops and transitions with the 18m and 21m.
Things go well if I keep the kite out of the water and winds are steady. I can usually work the kite and keep it out of the water, if the kite gets wet, then I most likely will be swimming to the beach.
I know that most people are using smaller kites when hydrofoiling and it get it. I prefer a 13m kite and only reluctantly pull out the bigger kites when needed. It is really these very light winds that can be a challenge and I understand that these big kites have a very small wind range. Maybe something like 5-6 knots with the 21m, and 7-8 knots with the 18m. Obviously both kites get overpowered quickly when you are moving fast on a big wing. That is the frustrating part, I can be very nicely powered up in 5 knots if I can get going and stay moving.
So, let me know how you guys are handling transitions in 5 knots?