Let's say 50% of people in Mattoon go to church. My guess is this is too high, but conservatively, let's say 50%. (We should probably do a study to find out -- how many are in church on a Sunday? What is their frequency? Do people usually attend every week or every other?)
With a population of 20,000 people, that leaves 10,000 people not in church. Let's further say that these people are identified as not having been in church for one year. Is this true?
Let's let our immediate goal be to get 1% of these unchurched people into the Crossover. That is 100 people. Our attendance at the end of this goal should be at least 125 per week. They won't come every Sunday.
What if our secondary goal was to get 10% of these unchurch people into a Crossover ministry? That is 1000 people. Just 10%. Just a fraction of them. Now note I changed the phrase to Crossover ministry. I don't think our goal is to have an attendance of 500 or 750. We want our worship services to feel like a known community. This might mean that we need three more Crossover type churches or maybe it doesn't mean they are Crossover churches at all. It is just our goal to expand the Kingdom of God in Jesus Christ with this 10%.
So this breaks down into three areas.
1. Identify who is in church and by that figure, figure out how many are not in church.
2. Attempt to bring 1% of that unchurched population into the Crossover church as it is.
3. Attempt to bring 10% of that unchurched population into a medium sized congregation (125-200), starting new congregations as needed.