0.02 btc per week for hero members is very less. You would have to increase to 0.03 and above per week. What you can do is increase the post or increase the pay per post to increase the btc which will help the best member to become part of this campaign.
Maybe some people just prefer to have lower minimum post requirement, maybe that's why this campaign had all the spots filled within few hours.
That is a very solid argument - I guess a lot of people like this style - that is why it gets filled up so fast, and we have to turn dozens of people away each week.
Alex