I would spend lots of time developing the kammback before fabricating one.
You need to simplify the installation and mounting method to a point that no one could improve on it, at least without great effort & Knowledge.
Off hand I think silicone mounted would be enough, if you gave it lots of surface area to adhere to , and designed it to be self supporting (hooked in rain gutter etc.). My Aftermarket rear top of the glass roof spoiler is mounted with silicone as per instructions.
Ride a Mtn bike for errands exercise entertainment and outright fun