I did this recently on my '18 SL. I didn't have any issues with the installation, nor the wiring. My only suggestion is to mount the horns under the main "radiator" core support (or where one would be mounted, on either side of the HV cables coming from the charge connectors) using the supplied bracket and some 1/4-20 bolts. I did have to use a "skew driver" and impact style drill bit to get in such a cramped spot but it makes the install completely hidden once the trim panel is reinstalled. As a bonus, they point forward for maximum effect.