Squeezing just a little more performance out of Core Animation

Question

I have a game that's moving fewer than 10 small animated UIImageViews at once, maximum. I'm driving their animation with a CADisplay timer running at 60fps. Here is an example of how I move the views in my update method:

// for each insect in insectArray
insectView.center = insect.hitCenter // I pull a position from my model object

The graphics are 32 x 32 pixels with up to 5 animation frames each, if that helps. They have an alpha channel for transparency. I've profiled and eliminated any in-game calculations as a bottleneck. I've also made the opacity property = YES, for a very small speedup. Having the animated frames playing or not makes no difference.

The frame rates are mostly great, except on older devices like the iPhone 1G and 3G. There I get intermittent stuttering.

Before switching to OpenGL, is there any way to get a bit more performance?