AA, I keep saying the same thing when these things come up, and I would like to repeat my advice in this thread as well.
Just get the PJ first.
Then what I always say is fire it at the blank wall. However, in your case, from the little I remember, I would use some spare bed sheet or something to tack up, and fire on that. Maybe fold over excess length of sheet, pinned to itself for better "accuracy".
While its a little annoying to wait those extra few days to order the screen, and it does take just a little more work, the surety you gain will be well worth it, IMO.