Rear window in the WOMO box car with or without order?

Hello dear forum, we family two adults and two children would like to order a WOMO van 3.5 T. Here we came across the limits of the payload and ask ourselves therefore whether we should order rear windows for it or not? These weigh together 8 kg. In the rear side we have already left and right windows installed. Since we have a raised roof the windows fall away as well in the roof. At the end we have already installed beds. We also use no bicycle carrier! Have you had any experience with rear windows (which are in the doors) or without windows? I am aware that without windows it will become darker or with windows it will become brighter. For example, if it disturbs when sleeping, is it better if there are fewer windows there regarding heating up? I am grateful for any advice! Lg