Originally Posted by Square Eye
Drywall is not necessary. I wouldn't recommend adding the weight.
You should be fine, keep your boards straight and check them with a string occasionally.
I agree 100% with Square Eye but there are a few things I do in this situation.
1- I snap a few chaulk lines for reference so I can check for straight.
2- I always check the wall and ceiling to see how straight they are.
3- check the meaurements from wall to ceiling so I know what size of board I will end up with when I get to the end so If I need to rip one down to get a even look I know what size to make it. Nothing worse than ending up with a thin piece.