It would reduce the range the detector can pick up. There are a lot of variables but in general it’s not the best place to mount it. It wouldn’t make false alarms. What band was constantly going off? Also, you can’t just throw a radar detector in the car and run with it. I found it’s best to learn how the detector acts around certain bands. Some security systems can set off X and K band. Some road work signs use K and maybe Ka. Fucking toll booths set off my laser sometimes (gay). And if a cop is way in front of you or behind you it might just detect them intermittently and you would think it’s false.
Good rule of thumb: If Ka is going off, slow the fuck down :lol It’s a very good chance it’s a cop. I almost don’t even care about K band anymore. At least not where I drive.