The owner who built my X Air had 12mm bungee cords on all 4 attachment points - all of which had different measurements! Some cords were 50 inches long while others were 44 inches long. That's why the left pilot seat was always sagging.
I replaced all 4 pieces with 10mm cords at 80 inches long for each piece - the suggested 60 inches didn't seem robust enough. The suspension sag and rebound is incredible now - and since I have lots of cord, I can always cut and remove cord as I see fit.
The cord was only 60 cents CDN per foot. Totally worth the $40 cdn to replace.
