afni.nimh.nih.gov

Hi AFNI experts,
I ran 3dClustSim with my data and found the cluster could not survive at p=0.001. But it could survive at p=0.002.
I remember that Cox mentioned the threshold could be loosed to p=0.002, but I can't remember more details. (Bootcamp at ShenZhen last December)
Could you please tell me where can I find the reference for choosing p=0.002 so I can use it to support my study?
Thank you very much!