Rick,
Thank you very much for your responses. One more question on AlphaSim , with regard to the choice of the gaussian filter. I am using a brain mask (vox dimensions 3x3x3) with the same vox dimensions as my resampled maps. The line command is:

AlphaSim -mask 3402.3spgr.mask1+tlrc -iter 10000 -rmm 3.1 -pthr .01 -fwhm 3 -out as.out

My understanding is that the fwhm should be at least the dimension of your vox (e.g., 3) or greater, and that the greater the number the greater the cluster size you will need to achieve the desired family-wise p vaue. What would you recommend given my parameters?
Is there a more precise guideline for picking the appropriate fwhm value? Thank you very much,
Alessandra