I unfortunately can't remember if changing resolution in the orbiter or the device tree changes anything. My mobile phone has a resolution of 800x480 and under Orbiter I have no size selected (it says "-Please Select-") and under the device tree in the child device I have it set at 800 (width)x600 (height) - most likely default. I don't remember changing those so I guess the phone stretches appropriately or something as my image is perfect. I'm afraid it doesn't help you all that much but it's the best information I can give at least. Play around with it I guess.
Also make sure that, under the orbiter page, the proper UI is selected. I've got the default running there, again, which is "Normal Horizonatal (3:4)". Don't ask me why that works, I don't know
I haven't played that much with the skins when it comes to Android. I've only played around with it on the JavaMO where things are just as confusing ^^ But it works for me so I'm not complaining.