I was just reading the FAQ "How do I fit an OEM D2S HID bulb into option 5(H9 projector)" and came across this.
"Cut out the 25mm hole using a Dremel ,Carefuly place D2S bulb into hole, so that it rests on the backplate. Note how easily it slides in all directions"

What's the purpose of making 25mm hole? and I don't understand how it slides in all direction.
I was just test mounting the D2S bulb to exsisting hole and this is how it looks like. If I give enough force, I think I can make it sit flush to the plate.


It's tight enough to do this.



and it looks like this inside, note that it's not sitting flush to the plate. Do I have to make the space for return wire bigger or is it good enough?
inside.


To give little more blue tint like Mercedes Projectors, I understand you can just band the shield little. Anyone know how much do banding is required to do this?

The 25mm hole will create the 5mm distance that is required from return wire to any metal. Said that, it does not have to be circular as long as the 5mm distance is kept. But in most cases its simpler to make a 25mm hole.