looks great Tim, glad to see these methods being put to use.

I think you would find that if you supported both ends, deflection would disappear entirely. The floors in Switzerland and Schwarzwald too git a lot of stiffness by being secured around the whole perimeter, and the wedgind. I think your screws will compensate for the wedging, but end support i bet would do a lot.

Yes that's a flag, looks like the Swiss flag. i'm surprised to see the Swiss Flag without the canton flag as well. maybe this was erected around August first which is the national holiday

the Bush is the top of a spruce tree or maybe a small spruce.