I find very little degradation from scaling items up and down in Photoshop, you aught to run some side-by-side tests (I have) to see how little the image is changed- just go up, then down, if you go reduce then enlarge you are throwing away information, of course, as there is no way to put the inforamtion in 4 pixels into one, the reverse isn't true, however. I'd stay with even magnifications, though - 4X then .25X, or 5X and .2X and so on, not 1.5X and .66X. This system is also the answer to "how do I paint a half pixel wide line", too - as Photoshop will not allow brushes smaller than 1 pixel, but if you enlarge 4X, and use 1 and 2 pixel brushes you have in effect 1/4 and 1/2 pixel brushes.