, Magga.
Remember to prop the lids open each day for fresh air exchange, whether or not the day is suitable for a trip outdoors. If stacked, I'll usually lay the lids across the top in a catty-corner manner, and place the next tub on top, along an edge for added stability. If kept on the drier side, weight usually isn't an issue. On days that they can go outdoors, I usually add about a half inch, to an inch (depending on seedling size and type) of water to the tub and let the plants take it up through their roots. I also try to avoid wetting of the tops of plants and soil whenever possible to discourage damping off and other disease issues. I haven't experienced any of these issues, but I still like to practice prevention...just in case.
Have fun with it! It sure helps to beat back the doldrums of those transitional weather days.
