I don't know how thick the plate is but I have found that mounting plates to a block of wood or other solid backup material stops any vibration during cutting...making for much smoother and easier cutting.
I just finished a set of knife scales in Argentium silver with sculptured scenes and some minor gold inlay. Was very easy to work...especially easy on tool points.
I saw a post on the ACGG Forum today to the effect that Tom Turpin has died. Tom was a great friend to all of us as he put many of our engraving photos in the Gun Digest every year. I will miss Tom!