I forgot to mention earlier but I've changed wheels in my Berta.
16" ET30 was changed to 15" ET47 and tyres 205/55/16 to 195/60/15 accordingly
So I've gained around 0,004 sqm in frontal area and what's most important, wheels are less sticking out from the body. Now I'll be able to cover rear wheels much easier with less frontal area than with previous ones.
Another thing with Berta's new wheels is that those are easy to cover with smooth wheel covers.