You can ask nicely you know, its generally a good idea to start with and an even better idea when its a mod you're being a jerk to.

Now to address your concerns yes you would need an insulating material between the backplate and the motherboard assuming there are SMD's or SMR's or other protrusions including but not limited to capacitors, chokes, mosfets and etc which are not ground(ed).

I'll be sure to put up some detailed pictures of what I do for you.