"These are the rules and this is how we are going enforce them... do the best you can. Good luck and see you next year". That's the fair way. All of them know from the start what the standards are and the most clever wins... as he should do.
This would be great especially in issues like flexible devices. Since everything flexes more or less... the only standards you have are those tests. Who would design their cars to pass tougher tests just to be sure?