That's a good trick. I'll try that next time. But ultimately, I'm going to stitch the images that produce the best picture, whether or not they are part of the same set, if it's possible, and it certainly seems to be possible... a 21mm shot with seriously sloping horizon and two 25mm shots with a different levelling of camera does not seem to be beyond the capabilities of CS3's Photomerge. If I can copy and paste a few patches from other similar images to fill in the corners, then I'll do it to get the result I want.
I do the same except a hand with one finger at the beginning of the series and a hand with two fingers at the end. Helps to tell when one pano series starts and ends.
Very interested in trying multi focus stitching (any particular tricks to that one?)