Well, I confess, it wasn't a very scientific or exhaustive comparison, just me sat with a ruler in the car with the various sleds in hand. Mind you though, your comment that the slot sizes have changed could be relevant - all the sleds I have to hand are relatively old (between 5-10 years) except the Philips RC629 sled in the Renault which is only a year or so old. that is a pretty sloppy fit in the console, and there is a support bracket in the back to bolt on to to stop things flopping about.

Dunno, is there actually an accepted, DIN size then?