Ah yes. The plugin info that is published to the host, is created very early in the process and if you don't publish the parameters the host doesn't know you have them.
If you get the latest code and build it you have the option to handle the Opened event on the plugin root base class(es). At that point you can assign the host automation interface reference to the VstParameterManager instances. Initialize the parameters
in the ctors as before.
Check out the VS project templates (Support) for an example.
I haven't tested this fully, but I feel confident it will solve the initialization sequence issue.
Please let me know how you're doing.