Although I am assembling a T-Rex 450 SA, this question relates specifically to how to correctly assemble male EC3 devices for connecting battery packs to ESCs. Do your solder the male pins to the wires and then plug the pins into the back of the blue backshell (plug), or do you first run the wires through the blue plug, solder the pins onto the wires, then pull the wire/pins back through the blue plug until they are tight ?

Those things are pieces of junk. Just order some Dean connectors. they ROCK!!!!!