Oya,
If group analysis is your ultimate goal, you don't need to correct for multiple comparisons at individual level. In other words, 3dClustSim for each subject is unnecessary. Instead you run 3dClustSim with the average smoothness across subjects, and apply the minimum cluster sizes to the group analysis (e.g. 3dMVM) results. Unlikely 3dDeconvolve, 3dMVM does not store the clusterization information in the header, and you would have to set up the cluster size on the AFNI viewer based on the information from 3dClustSim.
Gang