On our Allied Seawind ketch we fly the national ensign from our mizzen topping lift, rather than flying it from a short staff on the rail under the mizzen boom where it would be at odds with the mizzen sheet.
The one problem with using the topping lift is getting the flag to fly freely. To do this, it needs to be free to rotate around the line. If you thread the line through the eyes of a pair of flag clips, the weight of the flag cants the clips against the line. This jams the clips and prevents the flag from rotating until the wind is strong enough to lift it completely. But if you form the clip eye around a short length of plastic tubing with a slightly larger inside diameter than the diameter of the topping lift line, jamming is prevented and the clip can rotate in the lightest breeze.
I found an appropriate bit of barbed tubing in my plumbing supplies, sawed it into two 1-inch lengths, sanded the inside edges a bit to reduce chafe, and wedged them inside my flag clips. To hold the modified flag clips in place high on the topping lift, I slit a length of stiff hose with an inside diameter a bit smaller than the line and wrapped it around the line between the flag clips. The hose should be slightly shorter than the center-to-center distance between the flag grommets. Push the hose as high up on the topping lift as you want the flag to fly. Tradition says it should be two-thirds of the leech length above the clew, but we just push it up as high as we can reach from the deck.
Sloops and cutters with topping lifts can also adopt this method of flying their ensigns to good effect.