I have ran enough of these to tell you the only way roots are not coming out is if you screen the shit out of it. That did not even work for me last year I just trimmed the roots when they poked out every now and then. I think people are just going to far with this your roots are coming out of the cup. As I understood it originally the spirit of the rule is so some one does not just fill the cup with hydroton and shred the cup up and drop it in a DWC and get a normal size plant. Have people take full cup pictures and trim the roots. Let's not over complicate a really cool contest. I think the best part of this is it is on a small scale and people can experiment and try new things that can improve thier skills in the long run.
I am sure
@Renaissance Redneck can correct me if I am wrong.