Most here know, but for those who do not, I also besides being a plumber also do building as well. So please forgive me for forgetting. I have to install a double bowl sink with a under mount sink. There is a deep bowl and a shallow one. If memory serves me right, the GD goes on the shallow bowl side, then arms over to the deep bowl side. How high to center off the finished floor is the waste set at? I was thinking 14" to 16" is what I used to do. If it was lower than needed I would use a 1-1/2" x 6" extension tube to compensate.