I got a new 300kg scale today and time to test the pull of kites and strength of the line. First test is the club's 3mm poly line:
The supplier is unknown and we just had it in the trailer. Using a double figure 8 as the knots for the loop and larks head on tie off point, the breaking strain of the line was 135kg. 
After that I tested using a crocodile grip and the line snapped at 70Kg inside the grip at the pinch point. 
​Below are photos of the tests. 

Cool Drone Footage of Otaki festival.