I have tested and measured to find the correct length, as you could see the tips had a "kink" in the middle because the span line was a tad too short.
Kite flies just fine even with the short span line, but it is not looking perfect.
It is correct on the 3 and 4 and 5 and 8 m2 (at least those I bought), but on the first productions of 6 m2's (they must have changed it on the new ones) the span line needs to be 2 inch longer (50-54 mm)
I just added a short piece of line to one end of the span line, fixed now.
But as I tested without as the last test, to see that the tips were standing correctly and straight both with and without span line, I have just flown it without ever since (lazy, why should I install it again), no issues.