Best way to adjust underside of car after removing skirts?

[Pixtro]

I've been working on a vehicle and I've removed the skirts from around the car that I didn't want, but what's the best way to adjust the underside of the car to fit the new body?

Here is the front bumper, can see where the skirt was and the underside matched up

Again with the side skirts

I figured I would just have to scale and move each part to fit, but thought there may be an easier way. Any help appreciated!