Forgive my ignorance but can somebody explain the differance between Semi-stagger and Full stagger engine arrangments. Is it that the Semi-stagger is just with one engine mounted slightly ahead of the other motor, while the Full stagger one motor is mounted fully ahead of the other motor and closer to the center line of the boat?

Niether are inline
Full stagger puts the engines closer to the centerline than a semi-stagger.
To do this they move one engine further forward than in the semi-stagger.
This also creates less cockpit space, in a 38 Lightning anyways.