Karel, I have yet to see any original German measurements for the railing, but for my drawing I went for 40 mm for the upper and 20 mm for the lower.
Not sure if you know, but were are several different styles of railing;
(Like in my drawing)
100% Large
50% Small
25% Small
Netting
5% Smaller
100% Large
50% Small
Netting
10% Small
100% Large
50% Smaller
No netting (Maybe they were going to add it later???)
10% Very Small (Looks like about 10 mm)