I had several pictures of the process of building the cowl but I lost them when my harddrive got corrupted (common problem on Dell laptops). And even being an IT person, it had been over a year since I had made a backup lol.

I used 3/8" balsa for the four sides. The engine to mount is rotated to 45 degrees. That was just enough to get the engine off of verticle and still have the muffler clear without having to have too much of the lower cowl open. Here are the steps I used to make it:

Cut the cheaks off the fuselage
Mount the engine
Cut a circle out of thin ply the same diameter of the back of the prop spinner, then cut the center out to clear the prop hub.
Mount the spinner and use a little CA to tack the ply circle to the back of the spinner with some small 1/16 or so spacers.
Make some measurements from the firewall to the back of the ply circle and cut out the 3/8 balsa to fit around the engine.
Once the rough shape is in place, permanantly glue the ply ring to the cowling and remove the spinner and engine.
Sand to shape from the squared off fuselage out to the ply circle