If you have a border-line profile(that is, strong but not a clear competitor at top schools) then I think taking a risk with an excellent paper at the schools which encourage sending in excellent samples is sound. But if your profile is already strong then don't risk it, other than for the required ones.
What I mean is if you're a quarter-back and you're 6 points down with 1min to end the game, then throwing risky end-zone long passes is a good idea.
Anyway that's what I think, but remember I'm an applicant just like you.