Hello: I am going to be building a new interior wall to enclose an existing room and make it a bedroom. I am fairly comfortable framing in new construction scenarios but I wanted to get an opinion on this particular project. I plan on leaving the ceiling drywall in place and screwing the new wall top plate right though the drywall into the ceiling joists; however, I don't know what the best way is to secure both sides of the new wall into existing walls (see attached image red circles). I don't want to open up the existing walls to add additional vertical framing if possible. Thanks in advance for your opinions and guidance.