Tails will only apply when the Program/Preset is bypassed. If you are loading a new Program without first bypassing the previous one, then Spillover will determine how long the previous Program can still be heard.
Sorry, but the global tails parameter is the only thing that will change how long it takes for the looper to fade out once the new Program is loaded.
You may be better off bypassing the first Program, or stopping the loop, instead of adjusting the Spillover setting for this scenario.
