So i've got 1 wall finally framed, and on to the next one.
The problem is that i need a soffit to surround the main drain pipes.
A contractor suggested i could build a 2x4 ladder frame attached to the joists.
and then take 2x4 from that ladder to the wall, and attach the top plate there.
And do the usual attaching studs to that top plate and a glued/screwed bottom plate.
SO the top plate is only held into place by the L shaped soffit.
$20 in parts, a saw and a couple hours of your time and it would be moved. Just flush a 2 gallon jug of pine scented bleach down a nerby toilet before you cut the line and make sure no one is using any water. Then you just cut the pipes add some PVC fittings with glue and what ever pipe extensions you need.