pixshift has been giving me issues for a long, long time. It finally came to a head, though, when nothing I did could make l001 "work". It turns out, when you do cross-correlation analysis, you're really only interested in the most correlated pixel, NOT the junk around it - the junk around it only provides a second-order correction. Well, cross_cor_taylor.pro, a tool from the solar physics community, does exactly that. And it works far, far better than my hacked-together pixshift code. A lesson I should always take to heart: don't rewrite code if it's out there. Of course, if I'd known it was out there, I wouldn't have rewritten it....