If you want to make a custom setting the default when you load a Logic plug-in, here's how to set it up:
Insert the chosen plug-in on a channel.
Set the controls for the plug-in as you wish.
Open the plug-in Settings menu by clicking the arrow in the upper left area of the plug-in window.
Select Save Setting As..., and name the preset "#default".
The next time you insert the plug-in, the saved setting will be the new default. You can repeat this procedure any time you want to change the default.