Well they’re supposed to have the same circumference everywhere. Maybe what you experience is that because they are so long, the remaining ring is harder to stretch and that’s why you feel more pressure there. Also, it might be because of slightly larger base girth. I noticed both when I tried 64s yesterday. They fit quite nicely but I couldn’t unroll them to the end. They would roll back up because of the base girth, only about 1-2cm though.