I want to install a hard click vinyl floor over an old hard adhesive cork floor. The height of the new floor should be 4mm so it doesn't build up as high. Now, I've heard that you should only install 10mm thick vinyl flooring on HDF board on cork floors because cork is supposedly too soft. This is not true, at least to the touch: no matter how hard you press with your finger, nothing lends itself.
What are your recommendations/experiences? Pulling out the old cork is not an alternative.