We have had a couple of bouts with mold under our mattress in the van after cold winters. With 5 people in the van, we produce a lot of moisture. We have wanted to do this for awhile and finally got around to drilling ventilation holes under our mattress.
We went with holes instead of a raised ventilation insert because we didn’t want to give up another inch of height.
We didn’t have to deal with mold under the bed in any of our other campers. It was probably due to the fact that we spent most of our winters in the desert which is harder to do overseas.
Love to hear what solutions have worked in your campers.