"Experimental" in AFNI-help-speak means that the program has not be used in a lot of cases. Which describes 3dLocalACF - as far as I know, I am the only person who has ever run this program. Any changes will only come when the program gets used again (by myself or by YOU), and issues arise.
The lower limit of at least 39 time points is from the fact that the first thing computed by the program (in each neighborhood) is the correlation of the central time series with every other voxel's time series in the neighborhood. For stability, I set the lower limit on the number of time points to 39, so that the correlations would have some meaning (e.g., with only 9 time points, what does correlation even mean?). Where did I get "39"? I just made it up.
