Thanks for the yield expectation suggestion. Would that be per cake, per roll? Or would that be over the course of 2 flushes? 3 flushes? 5? Does yield vary much between strains? Does it matter that I use Wal-Mart Brown Rice and grind it up with a coffee grinder into a flour or should I buy organic brown rice flour already floured?
I'm a little confused on the tubs and the polyfill/holes at the pearlite layer. If I'm using an air pump, I was considering the ones that are used in hydro that pump 8 outlets that could go one outlet per tub. It looks like about a dozen brf cakes per tub. Wouldnt that cause humidity to go way down, or is the pump just on a timer or something? Building my fruiting chambers is next, just planned on a room with shelves and tubs sitting on them so far.
Oh, for starters, i'm Glad you asking questions! good ones too! I welcome any intelligent, and honestly asked questions. I tried not to go into too much detail on my explanations, because i didn't want it to be ridiculously long, or too confusing.
It would be per cake per roll/flush.
5 grams is closer to average but on the low side. expect around 7 grams.
10 grams is optimum. the most you ever see somtimes is 11 to 12 grams.
Yeild is strain and genetic related. some strains yeild better then others. also you can "clone" better yeilding genetics that you find within a strain. Say one cake does amazingly well, and you get this picture perfect mushroom on that cake made by god himself. you could using a steril knife cut a small piece about the size of a grain of rice out of the middle of the stem, part that has not been exposed to air. then drop that piece into a "Liquid Culture" the growth from that liquid would be a genetic replica of that mushroom and can then be injected into more jars. Doing it this would get you better yeilds and faster growth. Its the way the pros do it. Its very comparible to using clones when growing weed. and using spores is like using seeds. "multispore" syringes is like a genetic lottery much like using seeds. you have an idea where the genetics came from, and know the strain. but u could still get a wide veriety of diffrent looking mushrooms. I'm not going to get into details about clones and liquid cultures just yet. but thats the idea.
I have always used the store bought BRF. But i really want to try grinding my own. any bag of brown rice could work. but if you can find the word "organic" writen on the outside, thats even better. if its not orgainic, there is a chance they sprayed fungisides on the rice crops, and thats pretty counter productive. lol
Ok, to further explain the polyfil hole, perlite layer. Its picture time!
You see those White Puff balls at the center left and right of the picture? that is a ball of "polyfil" Polyfil is stuffed animal/pillow stuffing you can find it cheap at most hobby/craft stores. The reason for using polyfil is that its synthetic and nothing can grow on it. if we tried using say cotton. Cotton is organic, and might invite contaminations. You see the white layer on the floor of the chamber? that is perlite. you can see that the polyfil balls are just above the perlite level. Perlite has a large surface area, and holds water well. as the water evaporates off the perlite, it creates humidity. thats why we use it. but u want to try to keep the cakes from touching it a much as possible, so i use jar lids. but you could also use a square of aluminum foil. Also u can see that i fit 12 cakes into this chamber. Although the center row is a little tight, to make room for the polyfill balls.
the cake in the bottom right you can see that it looks much more brown. thats because its the newest cake in this chamber. while the cake in the top left is much more white. It was one of the first cakes in the chamber.
Great intentions, but think things through more. 
