I have a hotrod Scout with the 20lb platter and 10.5" Classic arm. Same problem, ringing when tapped and on silent grooves or passages. My solution was to put small plastic washers between the headshell and my Lyra cartridge AND on top of the headshell between the top surface and screw head. A great improvement. Washers are on Amazon for cheap.
https://www.amazon.com/gp/product/B01N02UG1F/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B01N02UG1F/ref=oh_aui_search_detailpage?ie=UTF8&psc=1