Marcus,
If you go here...
http://www.powerwerx.com/techdata/assembly-anderson.pdf
you will find all the data you need for these connectors including how to disassemble and solder. Although all of the splice methods outlined above work they introduce one more failure point in your robot. Since this is primary wiring, I recommend you remake the cable and connector with the lengths you need. We remade some just last night using the 5900 high detent contact. One of our ratchet style crimp tools did a nice job on crimping the body around the #6 wire which we followed with a solder job using a large tip 45 watt iron. Remember that a good soldered connection is one that starts as a good mechanical connection.
You can also check out the family brochure at
http://www.powerwerx.com/techdata/SB50-family.pdf