I agree that the fixed positioning on the iphone is still problematic at times, but it only seems to remain a problem with when something is fixed to the bottom, like the pagePanel footer. If that's the root cause of this then perhaps the best thing to do is reopen the previous fixed position case and link this one to it.
If we lose fixed positioning, then I think we should look for an alternative because it's really important as a distinguishing feature of our layout components.

the tabSet headers also stick when scrolling on the contentPanes. This has been a problem since before the development of the tabSet component and the menu component as well. If we can eliminate the fixed positioning on the tabSet headers, then we will have fixed more than one problem. The vertical scrolling on the example of the small view is also showing this same tabSet header "sticking".

screen shot showing tabset stuck half way across the screen after the contentPane has transitioned into place