The older I get, the less willing I am to mess around with ladders, although your proposed method sounds reasonable. How would one go about setting scaffolds over that porch roof?

We have an old dairy barn that had German siding (similar to clapboards). Most of the 70-year-old boards still looked fine, but the ones that were replaced in connection with some modifications a few years ago started rotting almost right away. I was shocked at how quickly the new boards deteriorated. I'm sure cedar would do better. Last summer we re-sided one end of the barn with Certainteed's version of Hardiboard. It's not historically accurate, but that stuff takes paint beautifully. I am looking forward to ignoring that wall for many years to come. Painted siding would be a big change in the appearance of your building, but you might consider it.