I haven't mounted any under the mirrors, but in planning ahead to do so I looked at those PCA adapters an decided that they only served aesthetics so that the lights aren't mounted at an angle. I think that 1 extra long stainless screw (or threaded rod with nuts) with an aluminum tube spacer would do the job. The lights would still be adjustable in two axes (yes I checked, axes is the plural of axis but it still doesn't look right), just angled a bit to match the angle under the mirror mount, but you'd still be able to aim the light where you wanted it.