Except if they use the mounting system where brackets are screwed to the sides of the HU directly, then the thickness of the collar and the play between it and the sides of the HU makes a couple of millimeters difference.
On all european cars I've seen the sled has fit, but they tend to use a simple hole in the panel for mounting, instead of brackets. On my VW Polo it is a very tight fit, (you should've included some KY ) almost no need for the tabs...

/Michael