Seems like you're trying to overtime the problem of a coin having mutually exclusive heads or tails options. The only way to get feedback is to show your work to people. The only way to prevent plagiarism is to never show your work to anyone. I very much doubt your friends are going to be willing to read and sign an NDA for the privilege of doing you a favor; they will more likely be insulted by the request.
You must be the change you wish to see in the world. -- Mahatma Gandhi
I vehemently disagree that it's an issue that's strictly got two options. Also, you don't know my friends very well. I've talked to at least one of them about this since I posted this and he said he would be more than willing to sign a contract like that, protecting both of us.