I've done the same to my front bumper.
I've cut it all out and meshed it all and stuck a Cordoba splitter on the bottom of it

To stick the mesh in i first used fibreglass filler but being as the cordoba splitter was seriously low (i've lowered it 20mm and cant get my foot underneath!!!) the fibreglass filler cracked and the mesh came loose, when i caught it on speed humps [

!]
Now i've used clear silicone sealant the stuff you use for sealing baths etc. This is flexible when dry so theres a small bit of movement, which helps.
If you want i can email you a piccy of what it would look like, or you can hang on coz i'll be selling this bumper when i get my new one through


"The Not so Fast but Furious"