Slant crankshaft damper and pulleys

I thought about the damper rubber a bit. I expect the factory rubber hardens over time, so the natural frequency might be a moving target. I don't know what design standards exist for dampers and what studies or calc's the designers did to come up with the existing design. It appears a damper can be essential. I have read that some truck owners who installed an under-drive pulley on their new Hemi motor have experienced a shattered "toner ring" - crank sensor teeth integral w/ the crankshaft. They blamed the pulleys changing belt harmonics. But, these guys are obviously tuners so may rev their engines more than most. Probably doesn't apply as much to the rugged slant crank, especially the forged type in my engines.

I know the polyurethane calk stays flexible over time. I used it years ago in rebuilding a camping trailer. Many people use the same stuff to fill motor mounts (Google Images). One can buy it at Home Depot. It wasn't simple to fill the gap with it. I used 3 drill bits to keep the gap equal all the way around.