I haven't tried anchor in conjunction with physics sorry
but using anchor with scale inner has worked in my prelim tests
images
1) properties
<img src="https://dl.dropboxusercontent.com/u/86190469/prop0.png" border="0" />
left edge = window left because you want your platform to be the same distance from edge regardless of size
top edge = window bottom because you want the TOP of your platform to be the same distance from bottom regardless of screen size
bottom edge & right edge leave NONE
works for me and my text see
2)
<img src="https://dl.dropboxusercontent.com/u/86190469/prop1.png" border="0" />
*EDIT* in PHYSICS properties prevent rotation set to no so when item hits with physics your platform would start spinning around the origin(imagepoint0)
set prevent rotation to yes to ensure staying at 0degrees