Using -Rerrts or -Rwherr as input to 3dFWHMx

Hello AFNI experts, I’m running 3dFWHMx to receive cluster thresholds for 3dClustSim and I’m wondering whether it more appropriate to use 3dREMLfit’s -Rwherr files or 3dREMLfit’s -Rerrts files? I am using the acf values from 3dFWHMx as the input for 3dClustSim to calculate cluster size thresholds for multiple comparisons corrections in 3dMVM. I ran 3dMVM using 3dREMLfit stats.