@d-healey actually if I recall correctly, its not a problem for the Linkfile - as this lives in a user-based folder, the problem is the plug-in itself - which should go in the system folders
~/Library/Audio/Plugins/Component and ~/Library/Audio/Plugins/VST3
so (like you suggested David) I now place the plugins in the user equivalent
~User/<user name>/Library/Audio/Plugins/Component and ~User/<user name>/Library/Audio/Plugins/VST3
But generally - yeah you get to come across a whole range of permission based problems building your own installer...