I recently bought an flx28 with proview ducer. It was my understanding that the cone angle could be adjusted by the gain knob. My sporting goods dealer told me when I bought this unit that vexilar did away with that and now it's a set 20 degree cone up until 30 feet then it switches automatically to 10 degrees for anything after 30 feet. Can anyone expand on this? Is this true? Not much for anything out there to read. Or at least I can't find it if there is.