All this is new construction.
All the DWV was installed before the floor and walls. Vertical pipe to the toilet is 4" PVC. It was cut long and has been sticking up thru the subfloor as construction progressed. Now I'm up to laying the CBU and tile. I have a Souix Chief 886-4PTM that will fit over the 4" pipe (and has been serving as a cap). Looking at it now, I se that the hole in the plywood is just right for the 4" pipe, but too small for the hub on the flange. I'm not exactly sure how to cut the hole bigger, since the pipe's in the way. Suggestions? And, how high should the vertical waste pipe be cut off, relative to the CBU?