There should be nothing between the recessed lens board and the negative that would interfere with the lens. I doubt that the lens would have to rise enough to touch the negative, but there's a slight chance the slider built into the lens stage above the lens would get in the way of the lens. The slider is intended to hold a dark red filter that allows projecting the image onto orthochromatic paper, such as graded paper, without exposing the paper. VC filters are meant to go in the drawer above the condenser or in a below-the-lens device.