As Kyle said, what you are really doing is not syncing the
image but stacking it. You will need a video distribution
amplifier to take one
image and
send it to two projectors. On occasion, you will find that your
projector will have a "loop through" so that the
projector reads the signal and also allows the signal to pass down the through, unaltered. It is possible that you may see some delay (hardly noticeable usually).
The difficulty you will run into with a stacked
image for this production is that you do not have a solid surface and may run into an abberation due to the increased depth of the surface. Of course this depends on how narrow a field you will be able to maintain your
fog. You are then adding the challenge of using a mirror to increase the size of your
image. If you are not at the extreme
edge of your
zoom capability (which I assume you are using a
zoom lens because of your earlier comments of being an off the shelf
projector), you will add yet another complication to stacking your
image. You have to be very careful with your
image since you are projecting text since it will be very apparent if the
image is distorted.
I am in no means suggesting that you do not use the multiple projectors in a stacked
image, the production I am currently working on uses three projectors for a single
image and I am projecting on
scrim for part of the show. Just make sure to allow yourself plenty of time to get it right.
Again, if there is any way that you can do a rear projection set-up, you will increase your
image visibility immensely which will allow for not needing as bright of a
projector and probably eliminate the need for a stacked
image.