I can see that your system have a second "layer" between motherboard and the medal case, you can hide wires there,thats good.
You have a nice and trim system there.
Why you want to risk anything?
Well,if you insist and if you are sure that you know what exactly to do.
Then proceed with caution with your own risk,though is a good idea first to completely remove the motherboard avoiding any contact and damage,especially during drilling.