X3 on Shade's Forbes Road series. He also has a new one, "Dunmore's Folly." Just came out. I'm a bit biased because Mr. Shade actually made himself available to give me some tips on historical fiction writing. He's a really good fella, and quite dedicated to the craft.
I also really enjoy James Alexander Thom's work, having read "Follow the River" and "The Long Knives," the former about Mary Ingles Draper and the latter about George Rogers Clark.
Both of these authors have done their research extremely well, while still encompassing some really superb fiction writing.