This is for all those guys running ZEs on aftermarket management.
If you want a really smooth (not noticable) switching of your SC clutch try this:
Set an auxiliary output from your computer to come on when manifold vacuum is less than 8" of mercury (about 0.27bar or 3.9psi of vacuum) and go off when vacuum is more than 10" of mercury (0.34 bar of vac).
Now add this circuit in between the ECU output and your SC clutch relay
It causes a 5 second delay in switching the clutch off once ECU switches it off, just like factory. You can adjust this delay by playing with the size of the capacitor.
Note too that this circuit works if the ECU pulls to ground when active, also the final output pulls high when active.
I just wired this up and it works perfectly, you don't get a kick at all when the supercharger goes on or off, just nice smooth power.