Suggestion: could you provide an example submission, which is ideal for what you're looking for except for not being underhanded?

Benefits:

- More approachable to mess around with for newbies -- download the example and try to break it.

- More likely that you'll get submissions from experts who have time to implement the underhanded part but may not get around to putting together the boilerplate.

- More likely that submissions will get the general task right and look similar for parts that don't matter, making for easier review.

Drawbacks:

- Potential for too many cookie cutter submissions.

- Might lead people away from thinking about alternate server designs that are more underhanded.

Mostly I think this might be worth doing because of the second benefit -- you're asking people to do a bunch of grunt work even after they've figured out the core underhanded technique.