In reply to message posted by Bendychicken:
why not just stub the pvc up above floor level and just cut it flush after floor is finnished?no measuring, no thinking required.
You can certainly do this., but you will need a special tool, i.e. the Rigid internal plastic/copper soil pipe cutter…cost about $100 US… So, unless you do a lot of this work and already have this gadget, why not cut the stub to the right length?
NtP