Using iDisplay on tablet for FMC issue

I just downloaded iDisplay for my tablet and its working great, only issue is that when I try to make any window for FSX full screen on my tablet, the bottom third of the screen can't be used because it stretches everything out so its completely unreadable. It works fine for anything else except FSX windows. Anybody know why this could be? I tried the default resolution as well as the highest resolution in iDisplay but still have nothing.