This is for my home.
I am adding a half bath in a bump out. I would like to avoid a VTR in the bump out as it is near some upper windows. The new toilet will be be physically in line with the old with a sink upstream from there.
Mike, the way the bump out will be attaching to the house, it would be very difficult to get the sink vent over to the existing vent. Especially since the main stack is encased in 6" of sprayed icynene. I may just have to add another stack - as far from the windows as I can get it. But it would be nice to avoid it.