When you say clipping path, do you mean a vector path to a layer? Is the clipping path all ready created in the document, or are you creating it via script? If you just want to create a png, and it's a vector mask, can't you invert the vectore mask and or copy it to whatever layer you want to clip, then resize? You don't need a flattened image to create a png.
The clipping paths were already saved in the files. Their purpose in print, in this case, is the same as for the web -- eliminating the background -- and so I don't need to invert it (easier than my original intention of converting the path to a selection).
I looked around and found a function that converts a path to a vector mask, so I used that. It's easier, faster and less code than what I was working with. I was preoccupied with using a selection, when a vector mask would do fine, and in fact led to a faster and easier script. Thanks for pointing me in the right direction!
Great! We all get locked into one direction at times. I know I do. Glad it worked out.