I have both left & right mirrors mounted about 1 foot in front of the windshield base. They work OK there. I do need to adjust it just right to be happy with what I see. Remember that you don't need to see the whole car. If you see a piece of it there is a pretty good chance the rest of the car is there.
You also hear most cars as they come up along side. That and a quick over the sholder look and I've been fine so far (20,000 miles)
I also agree with Tim. It's your car, put it where you want to!
Harvey