well, there are probably lots of different ways to string your flowchucks, however the knot that i personally like best is a double loop not in the middle of the cord
http://www.neo-nunchaku.co.uk/nunchaku_maintenance.htm
here is where i originally found the knot
i used to use my paracord just looped through one endcap and knotted around the other, but then the end with the knot around it swings kinda funny - if you use the knot-in-middle method i find the spin of the chuck from each stick is alot more even - it also gives you a good spot in the middle to move your fingers around for a wheel or infinite finger spins 
Hi, thanks for the link to my site re knot tying issues, as an alternative to this type of knot and if you wish to try a single cord or double
try tying the knots the other side of each other, creating two slip knots that can slide to each end and tighten down, the exact length has to be worked out before you start with some trial and error or good judgment the final length should be right for you.
To use two cord just run your cord though the loops on the nunchaku once more and tie as above no knot in middle.
Make sure you finish the knot ends of well and make them tight.
Hoping, if you understand this you might make a video of both of these two methods.....And finally would you allow me to post your video re my method on my site? on this page....
http://www.neo-nunchaku.co.uk/nunchaku_maintenance.htmlet me know what you think..
Kind regards
John
Neo-Nunchaku Exercise Organisation