I've never faced the problem simply because I have never done a lollypop tang.
However, I have just looked through Byrd's "Gunmakers of Buffalo Valley and Greasy Cove" and Whisker's "Gunsmiths and Allied Tradesmen of Tennessee" and from what I see the thicker tang coming off the barrel is left flat and the longer, thinner, extension is either also left flat or given a very slight radius.
If I were making the gun I would do what I considered aesthetically pleasing, and if something "looked funny" I would somehow address that.
dave