What thickness of washer to use for a cut dedome SST-40?

Hello everyone,

I am wondering what thickness of washer (mm or inches) to use to cut dedome a SST-40 without too much tint shift and to keep the bond wires protected? Thanks in advance for your help.

Sincerely
AlexGT

BTW this method of cut dedome looks promising…

Apparently the drill bits are 0.8mm in diameter