I don't know about the billet grill inserts for the dodge Nitro but here's what I did..........
http://i484.photobucket.com/albums/rr205/ssttnn66/jeepforum3.jpg
I used rain gutter screen from my local home improvement store and used manilla folders for a template. Oh, and don't forget......lots of patients.
The screen was easy to cut with ordinary scissors like what you get in a cutlery set.
This was one of my first mods and it really cuts down on damage to the radiator and such
. You'd be surprised as to the amount of bugs and crap these inserts catch
. Keeping my radiator and coolers looking like new. Oh, ...and no increase in temp either. I don't know if there will be a problem in the winter with snow build up, we will just have to wait and see. Hope this helps.
Just do a search on this forum, I believe under the kj section.