You can see here that the top plate of the longest stretch of the wall didn't line up with a ceiling joist. We just nailed 2x4 pieces perpendicular to the closest 2 joists along the entire stretch of wall to give us something to secure the top plate too. This worked well, although i'd recommend using something thinner like a 1x4. These strips became a nuisance when it was time to finish the drop ceiling.