For those who have a Uniden R7 radar detector, the correct Blendmount or one that works is the BR7-2014. Just tell em it's for a 2020 BMW M3. Still battling with the damm plug....it is so tight back there. LucidJazz thanks for the tip with the cap and that hasn't helped yet. Also based on the location of the radar detector it works fine there too. I heard early on some detectors didn't work except the Unidens.
Do you have free range moving the mirror? I tried to use one of my old Blendmounts. It worked as long as I didn't want to adjust the mirror (let my wife drive).