I don't know if they are the same size as the Vic Slimline plates.
But I made a 25mm thick spacer, 50mm wide and 300mm in length which filled up the space on the front
drilled and counter sunk the screws to match up with original holes on the front stone tray
and then screwed the Slimline plate into that.
I mounted it in high enough so you don't see the spacer
and it comes out flush to the front as you can see in the pics.
As for the back that just fitted in OK
Moz