@kamran Thank you again.

@jsotola I would have to reiterate the entire plate context of the original question in order for that followup question to make sense. Knowing stackexchange, someone would close it as a duplicate and ask me to explain how it is different. So I would prefer to leave it as a directly related question in the comment.

Excellent. Thanks. A follow-up question if I may. When I visit sites where builders (not engineers) come to discuss the practical use of such plates, a frequent question takes the form "Surely we shouldn't be putting a nail in every hole of the plate, putting nearly sixty 8d nails in a 5-inch by 7-inch area?! That would make the lumber nail-poor and turn it into toothpicks". Is there a technical engineering term for "nail-poor", or a term for the number of nails of a given size that a piece of dimensional lumber can support per square inch, or something like that?

Yes, of course. But if the fasteners are those called out by the manufacturer, how does the Engineer of Record determine what load a particular plate/fastener configuration can handle? Are there ISO standards to consult, say? A given fastener in a plate of a given gauge can handle X load, and then there's some multiplier?

Thank you for the advice regarding the ST23 and the rough estimate. A follow-up question, please. Would the following changes help to counteract the rotation? Replace 11/32 BCX with 11/16 OSB for the gussets; increase roof pitch from 4:12 to 5:12; make the building narrower but longer, an 8' span?

And local codes only say "in accordance with standard engineering practice" or something like that.

Below 200 sq ft isn't covered by the local residential code.

Thanks for the idea. So, instead of a cardboard base, put another filter there so that air can escape from the bottom as well.

Well, I'm testing it out but will have to wait a fairly long time before there will be enough dust on the inside of the filters to know whether the fan is dislodging any significant amount of dust from the inside of the filters and sending puffs back out the fan's perimeter. The 20x20x2 MERV13 filters seem to have decent airflow. The air coming out of them causes a strip of paper towel to rise to about the 4 o'clock position and stay aloft.

Thanks for the reply. My main concern is that the static pressure inside the box would cause dust to flow out around the perimeter of the blades, even if gaps were sealed around the fan frame; that is, dust dislodged from the inside of the filters, not "free" dust that was just brought into the box by the fan. I wouldn't want "puffs" of dust to escape.