Open Casket - full body impression, some disappointment... Should I retry, or forward fix?

I'm fast running out of time to get 'open casket' into a state where it can be moved out of my daughter's bedroom, as she will soon be returning from university. I therefore decided to bite-the-bullet and have a go at a full cast.

I did a couple of test runs using a wet sheet. I had tried putting a blanket between the foam and the final sheet, in the hope that the impression of the polystyrene balls wouldn't show through. This was the case, but the final impression seemed very shallow and a bit unclear so I removed it again. The final sheet impression was good, but at that point I sort of lost my nerve... Getting in and out is very difficult without causing big creases where I inevitable swivel my bum, despite my attempts to fire myself vertically upwards like a sandhopper! 

The polystyrene balls are doing a good job of moulding to my body, so I decided to try simply laying a sheet soaked in plaster onto the existing impression

Handling such a large piece of fabric, soaked in 3kg of plaster (1l water and 2kg dry plaster) was tough, and not having to get into it made the whole process a lot easier, as it was already starting to harden as I was smoothing it out. 

All that said, I can't lie... I'm not very happy with the impression. I am trying to tell myself that it IS indexical, in the sense that I've used the plaster-and-fabric to record the shape left in the polystyrene beads, but it's not rich, interesting mark I was hoping for. The overall shape is really weird with very rounded shoulders and a small head.

I think I have a frustrating decision - do I forward fix using some sculpting plus a layer of PVA-soaked fabric to hopefully smooth things out? Or do I attempt a true 'indexical mark' using a second piece of foam, cut to more of a 'grave' shape and filled with polystyrene balls? I guess the 'correct' but distressing answer is 'both'... Attempting a second piece of foam is complicated by the fact that I don't have a base-board, so I'd have to cut the shape into the foam as an outline, and then fill it directly on the floor, meaning balls will go EVERYWHERE when I lift up the foam (successfull or unsuccessful). 

Of course, unless the impression above suddenly looks amazing, the perfectionist in me is going to force me to flood my kitchen floor with balls :(