Side skirts for aero gains

[bryant]

im working with a maverick. its used for daily driver use, drag racing, and has done 2 silver state classic challenges and will do more. first time their was no aero mods on the car and driver complained about hood flaping at speed and the car not feeling planted in the turns. second time i put on a front air dam and that stopped the hood flapping and the front end felt planted. the driver did say the rear end felt a little wishy washy. now the first run the trunk was full of luggage and tools where on the second run it was empty.

so im looking at a rear diffuser but the underside of the car is very messy with exhaust pipes and the rear axle. so to my question.
would side skirts help over come the messy underbody and allow a diffuser to be effective?

also if using side skirts should they be located along the outer edge of the rocker or inboard inline with the inside edge of the tires? or maybe both with a channel or boxed in?