[dnanian]

Of course, we "could", but only be simulating the entire backup... which would take nearly as long as the backup itself.

One way to "test" out your backup sizes is to use a sparse image. See how much data is really copied. Then, you'll be able to size your partitions appropriately.

But don't make it too close. Slack space is important in some situations -- we don't make a delete pass before a copy pass, which means there can be situations where there's not enough space to smart update a partition if you don't have any free space.

Note also that programs like iPartition will allow you to resize your partitions "on the fly"... this could be useful as you attempt to optimize the partition sizes.

Hope that helps...