Since you are in Sweden I would guess that the oil in your fuel is of great quality (fuchs, Aerosynth/save??) Why bother with more oil? I only use 15% in all my engines, it is plenty enough
The OP owns a OS 46 LA, this engine has a plain bearing crankshaft and perceived wisdom is that they need a little more oil for longevity
I would suggest that for this engine in particular boosting the oil content to around 20% with some castor is a good thing.