Ticki2 I don't mind the suggestions, and often there are (and will be) things I hadn't considered, so it can all be very helpful. On the other hand, as you imply, too many cooks can spoil the soup and there will always be many multiple ways of doing something. It is a balance and we are all involved.
There is a vent on the kitchen sink drain at the wall that I will be re-using. I'm hoping the bath sink and shower runs are short enough to not require a vent.
Good suggestion for the fernco fitting. I'll think on that.
I think with the trap and the drain stopper, I'll be okay on the grey water back-up, but I'm sure there will be alterations required on the final product.
Incidentally, I have retested pilot holes for screws, thanks to your suggestions and I think you'll be favorably impressed with my latest choice.
