I used a bench top belt sander to remove the fins, then a dremel to carve the design. The aluminum was a consistant density though and you can see where the fins were if you look really close in person. Even when polished up fresh the metal is a slightly different color where the fins were.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!