I was going to ask how about getting the envelope coordinates in the geographic SR (4326), but i'm not so sure I need that. Instead, I'm not sure I'm setting maxOffset correctly. In the viewDidLoad I add a featureLayer to the mapView, setting the maxAllowableOffset equal to a NSNumber property I have declared (we'll call it NSMaxOffset). Then I have registered and listen for the MapDidEndZooming and when I get that notification I get the map envelope view area, do the above math and set a new value to the NSMaxOffset property.