Just some random thought about holding the work.
Use black or hard pitch rather than red pitch.The red is too soft.
If your pitch pot or pitch is too deep the work sinks(not good) and on thin silver it makes it easy to cut through with your graver.Using a wood block with a thin layer of pitch supports the work better on flat work.
I use bondo on a wood blocks for odd shaped pieces like patch boxes,buttplates and the like.
Mitch yates