I get a different number depending which program I use, and I'd be curious to know if it's a type 1 a type 2 or a type 3 gold coin that Chase gave us the numbers for (I get a different number between the small gold dollar and the large gold dollar). I have been playing around doing the same thing trying to learn my new machine.
I was also expecting the larger diameter to have the higher VDI, but not the case. The type 2 and type 3 read the same. All tests on that file were air tests with stock factory programs, with the sensitivity set to 75 to quiet the chatter.