I think I may have mis-spoke - I was talking about the clamps around the tubes, not the brackets that connect to the screen. I think those are designed differently (tops and bottoms different), to provide a "lock" with regard to the force exerted on the screen.
If you look at the tube clamps from above, say, the left one, the part that attaches to the clamp bracket is about 9:30 o'clock, and the head for the clamp bolt is at about 4:00. (Remember - you can't use a digital watch for this exercise

). If you just flip the clamp over, it puts the bolt that attaches to the screen clamp at about 8:30 (closer to the tank, but it needs to be flipped to the other side, because you can't tighten it without great difficulty).
If I've confused you thusfar, I apologize. I think I'll try and take a couple of pictures, which will be like those "can you spot six differences" puzzles.
Having said that, I do appreciate your support.
Helluva list, ain't it?