I am the electrical mentor for team #571 and spotted that rule right away. We used the SLU-70's on all #6awg connections as shown by the figure specified by the rule book. To properly terminate wires with these puppies you need to use a soldering iron and a heatgun!
The heatgun made soldering a rather quick operation, although we needed to let them cool a while
before adding heatshrink tubing. I also agree that strain relief is a very important factor for success with these connections. Our batteries' and bots' connections have stood up to the pounding of two regionals so far and have no evidence of loosening.
Good luck to everyone going to Atlanta!
Dana Susca
Electrical Mentor Guru
#571 Team Paragon