Sonic Barrier damping sheets vs cork

I have a friend (Pete Curry, bassist/recording engineer in Los Straitjackets) who put down a cork floor (over concrete) in his studio. Sounds pretty good---cuts down on reflections, but is not too dead. So Geoff, how come no likey lead as mass damper? I'm about to put some little stick-on lead weights (like for wheel balancing) on the counterweight of my pickup arm to increase it's mass (so's it can be closer to the arm's pivot, thereby lowering it's effective mass). No?

In most applications I’ve tried lead it hurts the sound especially in the bass, makes it sound weird. And lead seems like SUCH an ideal material. Not too soft, not too hard.  Lol  Maybe you will have better luck than I.

Cork would not be helpful.

Why not good ol' Sorbothane?

Why not Sorbothane?  Mainly because Sorbothane is one of the worst materials ever foistede upon unsuspecting and gullible audiophiles. And it seems like the perfect material, right? Not too hard, not too soft. The only worse materials, if that's even possible, are lead and SONEX.