I tried the kite with the quad 4 and the 5th line, still the same problems. When the winds got above 11 the problem disappeared. I guess the advertised 7 is not true, for a heavy rider (90kg). I also noticed that it delivers the power abruptly then stalls.
I think you simply choke the kite so it loses power !
In light wind, it is important to sheet out a bit - where many less experienced do the wrong thing - and pull the bar - and then you "choke" the kite - meaning you fly at an angle of attack where it has more drag, and less lift (power).
So keep it flying - a high AR kite like the Dyno can generate LOADS of power when flown fast !
When the wind picks up, one can fly it "normally" and easy - but at the lower end, one has to fly every kite very "delicate" with feeling - and it takes a long time if not used to that - but you will eventually learn - just keep going at it
A kite has to "fly" (forward) quite fast, and is not a simple ineffective spinnaker or parachute - in light wind
I actually prefer these kites for light wind, as kites like this with a more violent stall is typically much more efficient and low drag (higher AR and a profile with higher L/D). But of course more difficult to master.
The opposite type is low AR kites, that sits deep in the window - they are forgiving and easy to handle but not performing at all...
I assume you are on a big raceboard ?
As otherwise it makes no sense with 90 kg in 8 knots