I don't use that lens, but I often mount the 25 Skopar on the X-Pro1 using a Fotodiox adapter. I love the combo for zone focusing with the focus click stops and optical VF.
The thing with the 40 is you'll have to use the EVF, and the X-Pro1 manual focus assist isn't particularly good. I recommend buying the adapter from a store with a good return policy, just in case. Or, trying it with a cheaper adapter.
Also, you might want to look into Fuji's M adapter. I recall there are some coupling benefit, but not sure about that. I think it's around the same price.
John