Where are the returns to the sump located, mine were to low and oil was being pushed up them, after fitting a one way valve on the catch can return and moving another to a tee on the turbo oil return all is good.
And returning your oil to the sump is fine, the only reason people think its not is because they see the oil that comes out of a non return can, in a non return system the catch can will fill with oil and moisture and also during the cooling proccess it absorbs moisture giving it the milky apperance, BUT, with the return to sump the moisture will be cooked off by the oil getting hot.
Its like the condensation forming inside of a car when you are sitting in it, the insine becomes warmer than the outside thus creating condensation, when you turn on your demister it evaporates.
There is a stiky thread with oil control in the Forced Induction section.