Funny, I had the same thought when I was reading the thread on cheating today.
I think you designed the courses so that there were two or three of the legs near the beginning of a course were different. Like A and B.
The main thing we did was get all of the participants to acknowledge and agree to follow the rules before the event. Think of it as similar to testifying in court. Before you testify, you are reminded to be truthful and you acknowledge that you will be truthful.
That won't prevent systematic organized cheating, but it does a lot to prevent spontaneous cheating (like blindly following another runner). I suspect it reduces the chances of systematic organized cheating.
Like Possum says, we also did some forking to help keep packs from forming.
I think ONA had a write up from Peter Godwin about the event where he talked about the efforts to create "fair play." From memory, I think he was pleasantly surprised that our approach worked well. And, I wasn't surprised at all.
Having to attest to something out loud can really make a big difference in compliance. That's the reason why some steps of flight checklists require a verbal verification or response before continuing on. It's really hard to lie out loud.
I'm not super involved with the Junior Nationals next year, but I'm close enough that I can suggest these things to those in charge. Thanks!
If there is interest, get in touch with me later and I can provide more details of what we did.
I suspect following is something that isn't considered unfair at all for some people. Sort of analogous to how Americans consider walking on somebody else's land to be a criminal offense, but Scandinavians don't think that way. A different mindset, and there's not really an explicit rule against following.