just my thoughts, I don't have that camera:
I read that the 45mm xPan has a 49mm thread and has equivalent FOV of a 25mm on 35mm film.
But I also read that it doesn't need extra thin filters, that normal 49mm filter won't vignette.
Still I gues that a 'normal' rectuangular hood with 49mm thread might vignette, if so, how about first a step up ring to, say, 55 or 58mm + a fitting rectuangular hood from the bay? ( e.g. 58mm: http://www.ebay.com/sch/i.html?_from...+hood&_sacat=0