Cook beans in boiling water 5 minutes or until crisp-tender. Drain and plunge beans into ice water; drain.
Place potatoes in a saucepan; cover with water. Bring to a boil. Reduce heat, and simmer 5 minutes or until tender; drain. Return potatoes to pan over medium heat. Add 2 tablespoons vinegar to pan; bring to a boil. Remove from heat.
Combine remaining 2 tablespoons vinegar, oil, 1/4 teaspoon salt, and pepper in a small bowl, stirring with a whisk. Drizzle beans with vinegar mixture; toss well to coat. Place beans on a serving platter; arrange potatoes over beans. Sprinkle with remaining 1/4 teaspoon salt, parsley, and bacon. Serve at room temperature.
This really wasn't bad...I'm not a huge fan of green beans but this is one of the tastier ways I've found to prepare them. I didn't have wax beans so the proportion of potatoes was increased, although it still seemed small. I also fudged the amounts with the dressing but the combination of flavors was good - I expected it to need sugar to take the edge off the vinegar but it didn't. This is a nice change from boring potato salad so I'll keep this in mind in the future.