You may want to consider sending the prize-payouts to the eventual contest winners of your contest winners, which by shortening the chain of custody, would ensure you have only "good actors" involved.
In other words, four winners here will earn a 50 SBD pool divested to their own contest's winners directly from you.
Good luck on your contest ideas, everyone.
It will be much less work for me to simply make four transactions, and if the ones running the contests are not honest, they will suffer the repercussions.