To very quickly show what I mean I've linked to a image put in by fellow member Dave Shaw on his 1/35 build of a Panzer IV.
See vertical stacks. Also if you look carefully on your rear plate you''l see two small shapes, like triangles it appears to me. I reckon those are location points.
Oh, and don't paint the fire extinguisher red, it would be the same colour as the tank to stop it showing up to the enemy.
Alan