Ju to keep things square can you not cut some scrap MDF to use as spacers, you are gonna have to use a Syare at some point, I suggest gluing the top, bottom and rear, as your pic then wait for it all to dry, then use 2 spacers to between rear panel and rearmost transmission line, and wait till dry, then repaet for frontmoast tl line then lastly add front baffle, personally I would curb my impatience and take 2-3 days to get them built, looking good sofar though.