To finish my basement ceiling without sacrificing ceiling height to a soffit, I intend to replace the copper drain for the toilet that juts below the ceiling plane and runs under the single header for the rough opening that accommodates the shower drain.
I intend to replace the elbow with a spigot closet bend to pull the drain into the joist bay (please see the notional drawing below). The trouble is that the header will be in the way of the raised drain.
I plan on removing the existing header, chopping the joists back beyond the closet bend, and putting in trimmer joists and a double header.
How do I wedge trimmer joists under the main girder? Does this plan sound viable?
This is the way things look right now (the trimmer joists don't exist):