Congrats on the new Speciale and welcome to the forum. Unfortunately the only options that really exist on the market atm are universal, so fitment is going to be hit or miss.
It will fall out if you are just using the outer ring part... just use a dry wall butterfly anchor, that's what I did...The RAM stem mount works, but not well. The fork stem is not a deep cylinder, just a ring; there is less for the rubber to grab and my radar detector wobbles. I need another fix.
I cut off the large rubber piece and drilled out the hole just to give a little padding for the stem so it's not sitting on the metal of the bike.Did you use this instead of the rubber piece?