Fist off, It would be very simple to go down to any Fire station in your town and take a close up picture of their emblem off of a fire truck for instance.
Then load into Designer... 1st problem solved.
Second don't waste your time using optimum setting... use normal...
I use normal on all my litho whether I use 1/4" or 1/2" and they seem to turn of well. Remember that depth is highly important and this is something you need to experiment with to get the ideal look. On some objects the 1/2 gives better depth of field. Attached is a litho carved into 1/2 corian.
Attachment 72187Attachment 72186
Hope this helps.