[ERA Chas]

Good thought on the silicone and shims.
Here's a thought on the pads.
Yes, the guys want soft pads on this combo for the street. Mine are Sierra's soft compound and even they need time to get up some temp on the street. They're very good when hot however and don't fade away. Maybe they get tired after 30 track laps but not in hard street use. A harder pad may only make the noise issue worse.
Your current pads may be slightly glazed causing squeal. I rub the pads on a flat surface which has 40 grit sheet on it to scuff them and remove shiney glaze where the resins come up. It has worked very well for me.
Best luck,