Never, ever, ever, ever, ever volunteer any answer not related to your travel, anything on your person, or anything with you in the customs hall. Even for these, stick to one word answers.
You may get more hassle, but the less you say, the better off you are.
As far as being "flagged", who knows. I doubt there are a huge number of people on this board (or in the world) that can speak to admitting to something like this willingly.
