As far as forced perspective goes, it really shouldn't be necessary. We've already had 4 willing participants who are 5' tall, so that should settle us if we assume we get even more in the near future.
As far as rough guesstimates, I've stopped worrying about giving deadlines and so on. It'll be done when it's done, but we hope to have something near a complete cut of the film by end of 2010.