I used the smart level to level out the cylinders. I had to raise the tail quite a bit. I guess it makes sense, but the engine is actually pointed up a little bit when the airframe is in level flight. I didn't measure it, but I'd guesstimate that the airframe was around 3-4 degrees nose down when the engine was level.

Here's a shot of my contraption in action. Some of the cylinders were definitely more difficult than others.

OK, so maybe I'm a bit paranoid, but before I actually drilled/cut any holes in my beautiful primed and sanded cowling I needed to convince myself that the exhaust actually exits the engine at a 90 degree angle. With the cylinders level and the cowling removed, I extended the plumb bob and checked for perpendicular with both a machinist's square and the smart level. It is square within my abilities to measure it.

A close-up of my little homemade contraption.

I must have laid on my back for 15 minutes trying to get a picture showing how well the exhaust stacks lined up with my holes. The parallax in this picture makes it look like the aft exhaust stack doesn't line up with the hole. Trust me, it does. I'm very pleased. I used a 2-1/4" hole saw to cut the holes. I'm hoping this gives me enough clearance.

This is really just a placeholder picture. I about stepped on this little guy as I was walking to the Porta-potty this afternoon. He was actually moving around pretty quickly. Certainly didn't move as fast as a spider, but was moving faster than I thought it could...

If nothing else, it gave me a chance to try out the macro settings on my new camera...