Wash potatoes. Put in a kettle and cover with salted cold water; bring to a boil and simmer for 25 minutes or until tender. Drain, cool and peel. Cut into 1/2" slices and put in a large bowl. In a small bowl whisk together the oils, vinegar,dill, mustard, salt, paprika, white pepper and pour over the potatoes. Add the pepper and 1/2 cup onion, toss mixture and marinate in the refrigerator for 1 hour. Stir in the sour cream,eggs,1/4 cup onion, salt and pepper to taste and chill, covered, for 2 hours min'm or overnight. Serve at room temperature garnished with dill sprigs and pimiento slices. Serves 6 to 8.