Extreme clutch shudder

Brewers is right on the money with pinion angle. Myself and another member both switched from autos to manual transmission. Couldn't even pull out slowly without the entire car shaking. So much that the glovebox would open and hood bolts backout. Checked clutch, flywheel, mounts... tried 3 finger and centerforce. Same issue. Talked to an old engine builder and racer near me. He immediately said, "Its pinion angle." I couldn't imagine it since I installed everything using stock mounts and springs. I bought Calvert racing 4 degree shims. Put them in, problem solved instantly. He told me that people do not realize how by even pulling away slowly how violent movement of parts are with 4 speed engagement.
This solved the other members problem too. I fought this issue for more than a year. Even thought about going back to automatic.