Ditching old fwhm-based inputs in alphasim to using 3dClustSim

Hello folks,

So years ago, for FWE-correction, I would first generate a map of the residual error of my groupwise statistical map by dividing the beta-stat sub-brik by the t-stat sub-brik. Then I would run 3dFWHM on that residual error map, and manually enter those values in for -fwhmx, -fwhmy, and fwhmz in AlphaSim.

Now I’m admonished to ditch AlphaSim and use 3dClustSim. Ok, so now 3dClustSim is admonishing me to use an -acf option since fwmh assumes (incorrectly) that fMRI smoothess is gaussian.

So, can I invoke my group statsmap directly in the 3dClustSim command, to be able to calculate this -acf parameter on the fly and use 3dClustSim?

If so, what is the command or syntax?

EDIT- I tried solving this by just adding -acf to my set of 3dFWHMx commands in my first script, to try to get adjusted numbers for fwhmx etc to use for 3dClustSim, but I can’t interpret the output of 3dFWHMx.1D