This is the full buildup of the beam pendants.
Starting at the top of the picture, the build up is WM 620 baseboard, upside down, then WM 54 crown molding upside down and finally a piece of 1/4 by 1 1/8 inch flat molding to finish the piece off.
In the back of the pendant you can see that there are scrap pieces of 1/2 thick MDF glued in to provide a mount for the WM 54. We decided to reduce the height of the pendants slightly by putting the WM54 inside of the baseboard, instead of on top of it. This also provides some room for error in miters, etc.
You will also notice that this pendant is now notched on the sides as well as the front. The side notches provide clearance for the original 1 x 3 trim that runs around the perimeter of the room. (And, no, you can not take the 1x3 down. Its nailed in behind the ceiling beams. So unless you want to remove and then reinstall everything, just cover it up OK?)
Because these are 'lower' pendants, the top edge is cut at a 12 degree angle, if you look closely at the picture you will see that the 'top' is cut an angle. This is necessary so that the front edge of the pendant fits tight up against the ceiling. On the outside of the room, the back corner of the pendant hits the ceiling 1st and it prevents the pendant from fitting properly.
We saved the pieces we sawed off of the 'lower' pendants and glued them on top of the 'upper' pendants to help fill in the gap between the square pendant top and the sloping ceiling.
We attached these by nailing through the sides of the pendants into the beam (where the holes would be covered by the perimeter crown) with 2 1/2 inch 15 gauge 'DA' finish nails.