There's a mouthful, isn't it? Okay, as for the suggestion, I believe the current "Height Limit" for a parcel agent access restrictions is what... ground level + 20m? All fine and dandy on the mainland sims, as it'd really, really suck to be flying around a large landmass and keep running into parcels that one couldn't fly over at any height.
With the recent estate/region tool enhancements for private islands, however, I was thinking that it might be nice to have the ability to modify the ceiling of these access restrictions as part of those tools. I've been kicking around some ideas for a private island build, and the ability to restrict folks from getting within a certain distance of the ground over a parcel without being invited would be awfully handy.
(note that I don't own a private island, so if this already exists for private islands, someone can recycle these bits I just used up).