oil cooler and engine oil capacity

I was pondering the result of adding a .6 capacity quart oil cooler on my TW.. With the one quart stock oil capacity , would there be a problem of "flooding" the crankcase with an over fill of oil if the filter is above the engine and gravity takes it measure. If the system is sealed , I assume all is OK.. but with the crankcase breather , I wonder if the oil from the cooler would drain into the engine in places where it should not be...water seeks it own leval ~ maybe oil does...Thanks in advance..