In a 2012 harley davidson street glide can anyone give some advice on how to mount a hertz amp on top of the radio without it causing an issue with getting the outer fairing in place correctly?

 

There is an audio section here on the forum. My advice is to post there where the knowledgeable guys are.

My guess is amplifier selection is critical. I have an 800 watt Diamond under the fairing of a 2021 easy. I know you are more limited on space.

A couple of shops you can discuss this with are NVS Audio and Volunteer Audio.

Good luck