Just use this in your URI:
That's it. Not documented anywhere, mind you, but it works nicely.
This came up because it seems that google only like giving (roughly) 500 results back in paged results, which causes massive issues when trying to do something as simple as auditing a Google Site. Thus, you need to break everying into chunks, from the top down, as to minimize the size of things returned, while still (sort of) guarenteeing that you are going to get everything back that you expected. I will say that this small modification, as opposed to the "give me everything in one shot" approach, and setting the parent thusly, helped us go from around 900 results for a site (very wrong) to 5500 (more in the area we're looking for).