Hi Roger and all:
It would appear that the lessons I was taught may be in error. All sources agree, pith down. Proof again that: learn a lesson from only one source and that is what you know. Does not make it right.
Try wetting a shingle on the heart side then another on the bark side. Which lays flatter?
I am sorry that I passed along what I thought to be certain knowledge in error.

Unpainted pine board and batten (12 inch)has been known to pull nails and be almost impossible to even fasten when applied bark side out. I can show you cedar roofs that don't lay flat when it rains and I am sure the shingles that are floating and flying are bark to the weather.

But again, read and follow the directions of the manufacturer. Then check back in ten years to see if they are the same.

Great input Roger. Wood roofs are expensive, best kept out of the sun, but they do look great at least for a while.

Curtis