If I think I understand you correctly you could this plugin from Rex Rainbow
Easy to configure and you wont need to tween. Next, check out this video tutorial by ArcadeED
It will give you some ideas on how approach your safe zone when the screen is resizing.
I'm working on a game where the HUD stretches to with the dimensions of the device and I have a touch panel that slides out with buttons. Likewise, I have elements that are anchored.
You can see my games screen shots here http://www.neoprofessor.com/html/final_contact.html and notice that the HUD is stretched versus the video that's recorded on the desktop. Notice on the left side, there is the edge of the panel that when touched, pop out with buttons on it. You don't see screen shots of it but, I think you'll get the general idea.
Like everything else you need to experiment and find X and Y coordinates that will work for your game and you don't necessarily need to anchor it.
Maybe I'm misunderstanding you but, hopes this helps.