Well it might be but I have always used mine like a microscope as well without problems. Its magnification is such that the negative grain should be very obvious with trad 35mm film on a 5x7 projection. It will be a little less with Delta or TMax negs and less still with 120 Delta or TMax negs but there still should still be enough of the grain pattern to show.It is that grain that you need to be sharp.
Obviously set up the sighting line for whichever eye you normally use. It won't matter if both eyes are the same but a lot of people's eyes differ.
You mean It wasn't me I will try it again, and I will use your method. Thanks