If you are going for plastic body kit then no holes needed anywhere only 3m double tape and screws where you already have holes for mud flaps are more than enough
In case of Fiber Body kit it totally depends on the quality and shape n fit of the kit and panels
For side skirt ( fiber ) no holes needed you just have to place screws where the car already has holes for mud flap nuts
Even double tape is not needed because it doesnt adhere to fiber
Same goes for rear bumper skirt
You have to place screws where you usually have rear mud flaps thats it
