profiling memory instruments

I'm still looking for the best way (in terms of minimal memory usage and maximum performance) in making an app which is able to draw up to 50 layered PNG images in a scrollable view. The PNG-images have filesizes between 20 KByte and 450 KByte and image-sizes between 1500x1500 up to 7500x7500 pixels.

About two weeks ago I email a Tech-Support-Request to Apple, but still no answer yet.

Looking at quite a number of WWDC-Sessions and the large documentation set available from within Xcode, I still haven't found a good starting

point or clue in the best approach.

Hope that somebody can help me in this communicity.

My development setup: iMac 27" (16GB-RAM), latest Lion and Xcode and the target devices are iPhone-4GS/iPhone-5 and iPads with at least running iOS 5.1