To make something act like a fighter, it needs two things:
That needs to be added in to the list of all the other space behaviors, of course.
You can leave the space layer line out, because I think it defaults to fighter, but don't leave a line that says <Space_Layer>Frigate</Space_Layer>.
You'll definitely have to mess with the turn rate, roll rate, etc. and this is still going to look extremely weird for a ship the size of the Venator.
But hey, have fun!