I accidently found your website with one of my flies on it.
I would like to add a comment. The particular fly is very heavy leaded. It is designed to sink deep into the holes of my local river (Grindsted in Denmark) where we can see the graylings shoal in small groups. Often the riverbottom falls some 3 feet in the same distance, and the overall depth in the holes are easy 5-6 feet. Thus you need a heavy fly when your drift is only 6-10 feet.
Thus the fly is not a typical Czech fly. I do also have the slim type in my box.
I would categorize this fly as a “bug”.