My first Kung Fu instructor was a "little guy". I learned all about that real quick.
First the disclaimer: I wasn't there, and I'm no expert, but I'll blab on like I know what I'm talking about anyway.

I've been working on what Musashi wrote in "The Book of Five Rings" about taking on mulitple opponents. I've done some thought experiments, and worked things out in training and simulations, and expanded on it. He wrote about how he could take on multiple attackers by sort of working the corners of the group and pushing them all into one small group. From his perspective, as a single person, this does several things. The best place for my opponent is in front of me, the worst place is behind me. By pushing the corners in you keep threats from getting behind you. Another benefit is that you start "stacking" opponents. If you have three opponents, and they are in a straight line in front of you then they would have to fight through the guy in front of them before they could even get to you. If you can manage to move into a position that will line your opponents up (as much as is possible) it will give you an advantage. If they manage to circle you then you will be at a disadvantage.
Now let's expand that beyond Musashi's perspective (one Samurai vs. multiple opponents). Now we have 3 cops (good guys) vs. one bad guy. The worst thing for you guys would be to line up in front of him. The best thing would be to maneuver and surround him. If one guy can manage to get behind him and stay behind him then it opens up a lot of possibilities. It's all much easier if one person manages to get his attention. Many times people stay so focused on one target they forget about the other threats. That gives the other guys the opportunity to take up a better position. All of this takes teamwork and preparation. If one of you did manage to get behind him the old "grab his ankles and put your shoulder into their butt" works pretty well (I don't know, is there a technical term for it???). If you suprise them you really can take them down quick. The arms usually go out to break their fall. The other two grab an arm each. As you take him down, once he gets on the ground "crawl up" his back. This keeps weight on him while you maneuver for a better position. You can move up for the "knee in the back" or the 'knee in the back of the neck" bit, or get wherever you are needed next. Even if you are nothing but dead weight on his back at least you are making it more difficult for him to move.
None of this works without teamwork, so it takes practice. I usually have people practice two on one at first. Just maneuver. The two try to get in a position where at least one is behind the single person. At the same time the single person tries to get the other two into a straight line. Keep it walking speed only at first. This has two benefits, the single person learns to avoid a position of disadvantage while the other two learn to work as a team and get in an advantageous position. Then switch up so everyone gets a chance to be the "single guy". Then step up to 3 or 4 vs. 1. Then 3 or 4 vs. 2. It looks kind of silly, but it's easy practice and people really learn some good "subliminal" teamwork. After doing this for a while you'll just start changing positions without even thinking about it. It can work even if the other two team members aren't in on the drill. You just stay back and quiet and let them distract the person while you move.
I saw a perfect example of this on one of those cop tragedy type shows Fox is famous for. The car camera showed a Highway Patrol officer pull over a car load of guys. I watched as he focused on one guy and the other two surrounded him. What was he thinking letting them do that? Big suprise--one of them grabbed the cop's gun and shot him. Your feet aren't tree roots. They can move. If your opponents want to dance then dance. If anyone needs to practice this it's cops who work alone. Don't get surrounded!
I'm not going to tell you that I've mastered all this, I'm just saying it's worth experimenting with. Get your two buddies together again, and get some port sap to play the perp. Go through it again. Practice moving to better positions. See for yourself what works and what doesn't work. See if you can make the guy in the middle nervous. Making him nervous during training may make him nervous in a similar situation on the street. This might save his life some day. It takes you that small step from "I'm nervous" to realizing "I'm nervous because I'm being surrounded", which should then lead you to "I really need to move and take control of this situation."
I've had great success using this in training. We expand it by having multiple people with and without concealed weapons. Someone might come up and scream "WHAT TIME IS IT?" another might draw a rubber knife, another might draw an Airsoft handgun. People learn real fast how to keep threats in front of them, and how to walk around the perimeter of a group. The mere fact that you are not allowing yourself to be put into a position of disadvantage may be enough of a cue to your prospective opponents that they realize you aren't easy prey.
I haven't seen much training material on this, perhaps I've led a sheltered life. If you know of any sources of quality information on this subject (as it relates directly to CQB) please post them. I've seen bits and piece in different places, but nothing that really nails it.
Try it out and let me know how it works. I'd like to know what you come up with.