I am using the X100 with this combination of step down rings for a low-profile hood: 52-49 + 49-46 + 46-37 & cheap black 37mm cap.

It is very similar to what I was using on the Sony NEX 16mm lens:http://forum.getdpi.com/forum/sony/3...alternate.html

(to match the Pentax 40mm pancake lens hood idea)

So far it is working great.