Mounting Ceiling Fan to Exposed Beam

I am trying to mount a ceiling fan directly to an exposed beam on a cathedral ceiling. I will be running the wire in a channel mounted to the side of the beam.

I mounted a 1/2" pancake mounting box directly to the beam. The problem I am having is when I install the mounting bracket to the pancake box, then install the canopy, the 1/2" mounting box is not covered by the canopy.

I have looked everywhere for an answer to how to properly install a ceiling fan to an exposed beam like this, and I havent found anything that helps me out.

Any ideas?

Fabricate and attach to the beam a finish-matching or -complementary wooden block or box large enough for the base of the fixture, and also thick enough for the mounting box and bracket to sit flush inside it just as in a regular ceiling.

There are kits specifically designed for attaching fans to a sloped ceiling. Google "sloped ceiling fan adapter" to find a bunch of them, including http://www.lampsusa.com/index.asp?PageAction=VIEWPROD&ProdID=3773

My inlaws live in a log cabin, and on the first floor when the ceiling fixtures where installed, the boxes where cut into the exposed beams. You will need a good drill, wood bit, and a chisel to make the box fit.