I am sure I asked these questions in the middle of another thread, but danged if I can find it.

I am contact printing 8x10 negatives on the baseboard of my dichchroic enlarger. I put the negative emulsion side down on a piece of VC paper and cover it with a piece of glass. I set the head to the same height for all my contact prints and adjust exposure time with the lens aperture. I adjust contrast with the filters on the dichroic head.

Is this the best way? Is there something I am doing wrong? Finally, what is the best kind of glass to use, or does it matter (assuming it is free of any defects, such as bubbles or scratches, and clean)? How thick should it be or does it matter?

I know a lot of people suggest using a bare bulb, but that would require some work on my part, whereas the enlarger is already there.