Rear defence really required?

[shanetrainST]

Can the sit side by side right next to each other in the centre above the plate?

Preferred to spread them out.
The mainly target your Number plate and headlights. So having them just in the center is not ideal.

3 Heads on the front is the best option for protection.

Also depends on what brand of LJ's you choose too, some have better spread of light.

2 would be ok for the rear if you have a place to install them