I did a test with a friend, really it doesn't matter squat about the size or your scope Vs the size of the mask.
I had a 80mm batinov mask infront of my 10" newt and it still threw the diffraction spikes.
i had a 8" mask held at close to 2 meters from the front of my scope still throwing the diffraction spikes.!
happy days my friend. oh and as a bonus get a free program called Batinov grabber
makes life even easier!