iOS Splash screen transition flicker

I have been trying to get an AS3 mobile app that I built and released for Android to work on an iOS device.  I am having a problem with the splash screen on iOS, specifically when it is removed at the start of application processing.

My app needs to do some work on startup and so my intention was to continue to display the splash screen when I got control of the screen.  However, when my code starts executing I don't immediately seem to be able to determine the screen size accurately (I don't get a width of 768 pixels).  If I wait a bit (250 ms) using a timer then query the device Capabilities or stage width I get the right answer. 

What all this means is that I have to display a generic splash before I can display my platform specific splash and because it is necessarily stretched there is a bit of a jerk as the image changes from Default-portrait to generic splash to specific splash.  Is there a way to find the hardware platform and screen resolution immediately on startup ?  I am using:

screenX = stage.stageWidth;

screenY = stage.stageHeight;

var diagonal:Number = Math.sqrt((screenX*screenX)+(screenY*screenY))/dpi;

screenWidth = Math.min(screenX, screenY);

screenHeight = Math.max(screenX, screenY);

screenXMid = screenWidth*0.5;

I have also tried this with Capabilities.screenResolutionX and Y but stageWidth seemed more consistent.  Have I completely missed something here?