Check the existing ground clearance. You sure you want to bottom out every time you creep over a speedbump and enter or leave a driveway?
I agree. The ground clearance on a Prius is already very low for aerodynamics. Lowering or adding ground effects would be a mistake. Curious, is this something you are planning to do or is this market research..or just trying to get clicks to your site? Regardless, you might want to look around in the Mods forum.