X10 Filter Solutions
1.) Use dedicated Fujifilm filter adapter/hood with 52mm filters.
Drawback:Slots in adapter ring limit the effectiveness of a UV filter as a lens protector.
Note: The filter adapter/hood will fit the dedicated Fujifilm x10 camera case only without the hood attached.
2.) Use Marumi 40 mm filters. Drawbacks: While these work, the selection appears to be limited, I question how good they are, and they are an odd size which probably won't fit any other lens you may have.
3.} Use and S&W CO 40-46 mm adapter ring and standard 46mm filters,
Note: The adapter plus filter will fit the dedicated Fujifilm x10 camera case,.
I could not detect any discernible additional vignetting using any of the above approaches. I'm going with number 3.) because I already have a number of 46mm filters which I can use on the X10 in addition to the lenses for which they were purchased.