This model was kinda "quick and dirty" despite the hours of cutting - I used a skill saw to grind out steeper angles into a few strut points I cut too wide.
Mr. "I think I'm decent with Geometry" totally failed to notice the 3D compound angle bit, so the model ended up having struts that make "exterior shell contact" but not along the interior length of the strut face. If you cut each of the two cuts that make each pointed strut end with an 18 degree or whatever bevel, you don't end up with an 18 degree strut face. The online "compound angle" calculators appeared to be backwards, so Mr "I can has geometry" find L as a function of theta and X
looks like, L= x / (sin(90 - theta)
So if it's a 2x4" that's gonna be a B end (or 18 degree strut angle);
x= 4" tan 18
then use x and miter theta to solve for L, then set the bevel angle to give you L! If you don't piece meal it and actually solve for the proper bevel angle, the beam dimension will cancel out... Looks like the first solution is 9.2?
Since the foundation struts are half lapped, the first level of struts that sit on the foundation struts get a straightup 18 degree bevel, because they are sitting on a flat surface and not another cut strut end. However, the 90 degree faces needs the fix...
Next up, turn two "slightly wonky log end tops" into two precisely level planes and distanced vertexes. And then slap a stencil block on there and choose your saw.