In a large bowl, combine spinach, radishes, red onion, and cheese. For dressing, in a screw-top jar, combine oil, sugar, lemon juice, mayonnaise, vinegar, mustard, seasoned salt, and garlic. Cover and shake well. Pour about half of the dressing over salad; toss to coat evenly. Top with bacon. Makes 6 to 8 side-dish servings.