Just an update :
I dont collect any oil, water with a few drips of oil.
In 2000km the catch can is almost filled with water !!
All that moisture in the oil will be sludge/mayo and block the stock system.
I made an extra tap in the bottom with a very small hole, water can slowly drip out but not a lot of air can be sucked in to ruin feuling.
Offcourse those drips contain minimal oil and is bad for the envoirement but so is the powersteering fluid and other minimal leaking VCG's etc.