Hi, I have a flatbed 5x4 with a regular ground glass. For fine focusing I use a 4x slide loupe. But I think this is not going to give me correct focus since the image is formed on the other side of the glass and I am focussing the shiny side of the glass (thickness of glass is about 2mm).

Any suggestions on how to get around this. In India we dont get loupes meant for ground glass. Can I file off 2mm from the existing loupe - will it work fine.