Avocado Half-Shell with Marinated Shrimp

1/3 cup vegetable or olive oil
1/2 cup fresh lemon or lime juice
2 Tablespoons white wine vinegar
2 teaspoons capers
1/2 teaspoon dill weed
1/2 teaspoon dry mustard
dash cayenne
1/2 teaspoon salt
1 pound small fresh cooked shrimp
3-4 avocados, halved and peeled

Combine oil, lime or lemon juice, vinegar, capers, salt, dill, mustard, and cayenne. Toss with shrimp and chill, covered, several hours, stirring occasionally.
Brush avocado halves with marinade. Arrange on lettuce and fill with shrimp. Serve with remaining marinade.
Serves 6