Trevor might have more to add here Michael, but the extra space required will be approximately equivalent top installing a stripped down version of either package (MediaLab or DirectRT) and some additional Windows components if the user does not already have them installed (e.g., the .NET runtime package).

As far as subject and condition IDs go, our current plan is that it will work the same as it always has with the desktop versions. e.g., see:

http://www.empirisoft.com/support/showthread.php?t=26