Ducati Ignition Coils

I am trying to mount my dual ducati ignition coils (rotax 670) to the fire wall. I was thinking about making a box out of aluminum to help shield them so I don't get radio interference and for a cleaner look. Does anyone have an opinion on if making the box out of aluminum would be a suitable material to make it out of. Would say plastic be way better? Also, should I have any concerns with placing the two coils right next to each other or should they have sufficient spacing like when they are mounted to the engine? Thanks