I made a paper mock of the upper structure with all measurements times 1.25. Looks much better in my oppinion, will go with that size.
I then created the structure in OpenSCAD, to check how the struts would look in comparison.
The initially planned 5mm struts:
With 6mm struts:
With 7mm struts:
And with 8mm struts:
I have not decided yet which to my eye looks closest in proportion compared to the original I am trying to replicate, but the 5mm are definitely too spindly.
Also, I will probably increase the height, but that does not mean any fundamental changes to the design, just cutting the struts to different lengths, so that decision will be made during the building process, when I see the actual model.