turbo oil drain

hi all....
just wanting to know what size the oil drain back should be on a s475.I have a 1/2" drain back to the timing cover where the fuel pump used to be.

got my car up and running and been on shortish road trips to get afr's sorted. have noticed on start up and idle some signs of white smoke out the exhaust. today I found oil dripping on the chassis rail under the turbo. had a look up underneath the car and could see oil dripping at idle from around the v-band where the cartridge and hot side housing mate up.
did not smoke at all at first and now getting worse. turbo is new outa the box.
could this be because the oil is not getting away fast enough.

thanks guys