honestly....i've ran with my valence JUST being held on by the factory snap thingys on the 'ears'.
put the pieces on the valence, i like to pop the valence in the bumper one side at a time, then running the 8 bolts or whatever. factory,the bolts are like 8mm x 1.25 or someting....id probably be cheaper to get those Jnuts or whatever they're called in 1/4" and use 1/4x1 bolts.
the ears sorta snap into place with a gentle punch of the fist.
Here's a view of the inside installed on the bumper...
Here's a better close up of them..this time the side that has all four.