Cut each potato in half crosswise; scoop out pulp, leaving a 1/4-inch-thick shell; reserve pulp for another use. Sprinkle insides of potato shells with salt and pepper. Place potato shells upside down on a baking sheet coated with cooking spray. Bake at 450° for 15 minutes; set aside.
Heat oil in a medium skillet over medium-high heat. Add corn and green onions; sauté 2 minutes. Add vinegar and chopped tarragon; cook 1 minute. Divide corn mixture evenly among potato shells; top each with 1 shrimp. Garnish with tarragon leaves.