Combine the balsamic vinegar, olive oil, garlic, salt and pepper in a bowl and mix well. Marinate the mushrooms in the vinegar mixture for 20 minutes. Combine the crab meat, artichoke hearts, cream cheese, mayonnaise, lemon juice, worcestershire sauce, salt and pepper in a bowl and mix well. Remove the mushrooms from the marinade and discard the marinade. Grill the mushrooms over hot coals until they begin to get soft. Place them stem side up on a baking sheet. Cut each tomato into 5 slices and arrange on top of the mushrooms. Divide the crab mixture evenly and place firmly on top of the tomatoes. Bake at 350 degrees for 15-20 minutes or until the mushrooms are tender and the stuffing is heated through. Prep time includes marinating time.