[Zeke]

Personally, I'd have a hard time putting any wood on grade. However, the term "mudsill" came from wood placed in wet mortar for uniform support and load bearing. You could elevate your PT lumber on an inch of modified grout, like the epoxy stuff and know that water won't be continually attacking the base of your wall. Modified meaning waterproof.

Are you planning to bolt the sole plate down at all?

BTW, love the roses and the old driveway.