A couple of thoughts.
1. Don't forget to include the weight of everything you will throw in the tow vehicle when you are looking at the weight the tow vehicle can pull. Passengers and all that stuff in the back decreases the amount you call pull. People tend to forget that. Six people and luggage adds up.
2. Get a good tongue lock for times when the trailer is sitting by itself, either at the school or on trips at the hotel or venues. Some of the places we compete aren't the safest for a trailer. You might even want to get a Denver Boot to lock the wheels. Here is a site that has stuff to help. Don't know anything about them, just did a search.
http://www.universalboot.com/
For those of you who don't have electric brakes, I suggest getting them. It is an easy after-market installation job. Did it myself on my box trailer. Even a moderate weight trailer will warp front disk brakes on a tow vehicle if you aren't careful. Much better to have the drag of trailer brakes help slow you down. Much safer too.
Dr. Bob
Chairman's Award is not about building the robot. Every team builds a robot.