I've said this before, but I do not like mono tubs. I know they work but I don't think they provide optimal conditions for mushrooms to grow. There is no real circulation going on in mono tubs, you may get some evaporation but not much fresh air exchange. Also, all of the humidity for a mono tub is pulled from the casing which dries it out quicker. I use geolite with water to keep my humidity high and prevent moisture being pulled from casing.
I prefer a fruiting pan, placed inside of a larger container, raised an inch or two off of the bottom using a rack. This way the fruiting tray is enveloped by air and air is circulating all around your tray. This also creates insulation from the edge of your bin and creates a more stable environment. This also allows any gas to simply roll off of the tray into the bottom of the container and out the drainage holes. You only need a few air drainage holes in the bottom of the container and a few at the top to get decent circulation. I also don't understand why people make holes and then stuff them with polyfil. I never stuff my holes with polyfil and I use smaller holes than pictured. I hope this helps and let me know if you have questions.
Yes, a mono tub gives you more growing area but I prefer healthy and happy shrooms over a little more growing room.
