I constantly go out in contitions between 20 to 30 knots (Averaging 25). I ride an 11mt foil kite and a race hydrofoil. My limiting factor is mostly really gusty conditions, where it becomes night impossible to get set on the foil and keeping the kite steady becomes a struggle.
Based on your comments and video I think you are under estimating wind speeds. (Did you have a reliable wind station a few meters up with these numbers?) Based on the other tube kites in the air I think it’s very fair to say it’s likely to be above 8 knots. Also the difference between 6 and 4 knots...
With the kite opened up i put all the briddles in up to the conecting lines, leaving only the bar out.
Then I roll from both tips till the center (like a normal LEI)
99% of the time i get no tangles
What I did to both my 11 and 15 is to extend a bit the z line a couple inches to let the kite move a bit more freely, it did increase both turning speed and acceleration.
I m flying my sonic 3 11 with 11 mt lines, and loops with no problem. I ve tried with longer lines as well, 15 - 20 and 24 mt
but above 15 there seems to be some lag in the response, so i stuck with shorter lines.