I've seen similar mods using a keyboard cable but because of the superiority of the twisted pair cable in a Cat 5e patch cord I've successfully synced flashes from as far away as 30'. I haven't tried going further.

Included is a patch cord - I think 15'.

The original Canon cord is worth about $50 but this mod just might make it priceless :) To the right person of course!

On the camera end the mod is very polished because the network port fit nicely into the original casing. On the flash shoe end the original 2' of coiled black cable is punched down on the network port and then the connection wrapped with linerless electrical splice tape which makes a nice watertight connection but does not look as polished.

I'm selling this and some other Canon gear because I'm moving to Nikon.