You will find soon here some helpful tips on kite lines DIY, tuning and maintenance. 

Kite line splices and methods for splicing: standard sewn splice, Brummel locked splice. 

Splice length and taper.

Sleeved & sewn loops.

Line stretch/elongation and shrinking. 

Abrasion resistance and strength loss.

Air drag - diameter and cross section shape. Whistling/vibration.