I tried the "Stunt kite spar fitting (4mm)" by Hassan_Helal", which is a great design, but did not print that well on my Printer when using flexible materials like TPU.

Also, when printed in the TPU I have, the connection to the outer spars was not solid enough.

So I remixed that design, firstly to fit 5mm spars as used in my kites, secondly to have a solid connection on the outer spars (A real pain to fit but now nearly indestructible) and finally added some support structure that needs to be cut-off after printing.

The prints after that came out way better in TPU and is VERY robust. Wont ever be replacing these again I think :)