The photoshops below have been revised in light of new evidence that appeared in July of 2011.
Other new material is in pink, reflecting an update in September 2013.
In evaluating the thematic cohesion of the original attic, in which the two blast-up ghosts foreshadowed the Hat Box Ghost, who in turn was husband to the Beating Heart bride, I thought it would be helpful to re-create the original bride in her original position as much as possible, showing how the second blast-up may have looked positioned directly in front of her.
It should be stipulated that it is possible that no blast-up was in that location when the HM opened. The blueprints show that as of May 1969 there was no popup planned for there. They show instead a popup at the right side of the attic exit, just inside the attic. I have no recollection of that arrangement, and I suspect but cannot now prove that they decided to move the popup (a blast-up type) to its position in front of the bride before the ride opened. A blast-up was in that spot until Constance showed up in 2005, and no one seems to remember a popup by the exit.
According to Tony Baxter, documentary evidence suggests that "a lot of drapery material made from transparent plastic" was there with the bride. This was discarded entirely when she was moved across the track to the Hat Box Ghost's vacated position.
In reality, we now know (thanks to new evidence rediscovered in August 2013) that between the two attic posts in front of her was stretched, floor to ceiling and post to post, a sheet of plastic or nylon, and perhaps this is the fabric that Tony was referring to. It probably would have served the purpose of making her look cloudier or distorted. This accords very well with my personal memories, which I described in 2007 like this: "Well, when we saw her there 8/14/69 my brother and I both thought she looked murky. The fabric [of which Tony B spoke] plus the figure plus the adjacent wooden attic structure almost made her look like she was standing in a doorway or cabinet or something. My theory is that they were worried that a simple figure so close to the track would just look like a mannequin, and they deliberately tried to obscure her a bit." I suppose now that it was the plastic/nylon screen between the attic posts that gave an impression of her standing in a cabinet or doorway.
There are no photos, but some murky film footage emerged in July of 2011, and together with other clues it was enough to establish that this version of Beating Heart was the "Corpse Bride" version. I've worked up a pair of photoshops of the scene, one with the blast-up hidden and one with it in sight. If this is indeed what was there originally, the way the two figures were arranged violently juxtaposed them. Their relationship would have been made clear by the Hat Box Ghost.
Just to get your bearings, here's the same scene pre-Constance, in 2002. Note the piano on the far right, added in 1995.