With the info available on this thread, it looks like the answer is around 14 relpys/religios thread. Thanks for all of the input.
Now, in order to determine statistical significance, if any, I highly suggest you apply your National Geographic magnifying glass to responses on Free Republic as a whole.
What is the average for that whole, compared to the subset? Is there a meaningful variation between the two? Would you deem the entire forum unnecessary if it fails to meet some arbitrary measure of success as defined by ... whom? You?