Looks great!! But how well will it stand up to a serious rock strike?
I don't do a lot of off road, but I do find myself there sometimes, eg Meat Cove, Mt Washington, and if something is seriously rocky, two things: I am not there, and if there, I am not going fast enough for a significantly ballistic strike, any more so than gravelly paved backroads.
But, to answer your question...I thought about that before install, and I thought that no matter how rock proof any grill may be, God will always find a way to make a sharp rock better than any grill. In the meantime, just an extra layer helps by the quarter inch holes in the grill, and because it is a bit away from the fins, it will "give" a smidge when struck, diverting and lessening the angle of attack, dissipating the impact force of any stone by spreading it out over a much wider area thus allowing the radiator itself protection. As I said, there is over 10k miles now on the grills and they seem to have worked perfectly thusfar--no dents in them, no rocks of pebbles embedded, no affect whatsoever on engine cooling.
Living in the deep south, I was very concerned about engine heat management and many of the grills really cover a LOT of the business end of the radiator. They have to inhibit airflow and thus cooling, it's physics: no airflow, no cooling, IOW no radiator. That was as important to me as the rocks thing. And there was the cost thing. The site linked has many styles of grill material, some much more occlusive than others, but all relatively cheap.
Admittedly, some people just feel more comfy with "Alt-Rider" or "Touratech" or "EBAY" written on farkles and mods, and some just don't trust themselves to fab something. And that's fine--we're all in the same club, but for me, and many other BMW riders, esp the GS flavor, I like to tinker and really like to save $$$$. Many like to dig in to the guts of the bike, and many don't.
In truth, I think my design is better than those cut out sheets of aluminum with fancy laser guided cuts, displaying someone's logo. What it may lack in strength compared to sheet metal, it makes up for in allowing cooling, and by design, it appears to be strong enough.
Obs, ymmv. IN a way seeing these mods makes me think about their importance, and how to make one myself, if I choose. As Richard Powers has twisted the phrase: Invention is the mother of necessity.