less to do with resonance and more to do with being non-magnetic. Be very careful with MDF as it will not tolerate many screw swaps before it is stripped then you are up the creek
Cheap tweak from Virtual Dynamics:
Has anyone seen the short video from Virtual Dynamics showing the owner replacing all his speaker screws with all brass screws? I was wondering if you could hear an improvement. It's a cheap tweak, so I thought I might go to Home Depot and try out a set. What can I lose?