You can do that (resample the image at a new ppi), but it does degrade the image, and you have to mickey around with it to get it right again. I did it with one of my images that was published, and it came out not too bad, but I did have to make adjustments to the resampled image, otherwise there is some pixelisation, depending on how much it is resized. The best thing to do is render at the desired ppi and output size. What I do, that works very well, is render at the second largest size I plan on printing (I like to have a choice of sizes available), usually 8x10, and I will resize the final image to 5x7 and 11x14. If I render and work at 200 to 300 ppi, this works out just fine. All I have to do to the resized images is run them through the sharpener a bit. If I were to try this at 72ppi...they wouldn't come out as nicely, and I'd have to do some serious filtering to get them to an acceptable quality.