I found a really great example app by Apple to implement Infinite Scrolling using a similar idea in the OP. Very simple and most importantly no tearing.
http://developer.apple.com/library/ios/#samplecode/StreetScroller/Introduction/Intro.html
They implemented the “content recentering” every time layoutSubviews
was called on the UIScrollView.
The only adjustment I made was to recycle the “tiling effect” instead of throwing away old tiles and allocing new ones.