The real question is why are you putting on Mud flaps . The Back flaps are to protect the driver behind you and if it does not get down close to the road it gets missed by the spray and debris.
If you are interested in protecting your own vehicle then the important flap is the one behind the front wheel . If this flap is big enough it will protect all the important stuff between the two wheels. The door bottoms the Rocker panels and the lower slide door track assembly, Brake and fuel lines
Do you live on a Dirt Road .
Nice could have a different Definition.