P33...
Barb Tewksbury made me a kilt that ended up with the same issue. It was no fault of hers. If anything, it was my fault in measuring differently than she usually does. I looked at Alan's thread about the SWKs and that they don't have the same shape left and right....I would definitely look at that and see if an iron can solve the problem first.

Assuming the apron does have an "A" shaping, the problem is caused by your thigh circumference as compared to your hip measurement. I have large thighs that require different shaping through the waist and hips. Instead of a somewhat standard A shape, I use more of an hourglass shaping to my aprons. The fix in the kilt that Barb made for me was to undo the first pleat and reshape the left side of the apron edge. This is not, by any means, a quick fix as it requires undoing the lining and the pad stitching, etc. When I had the occassion to take the kilt to Barb after I had done the alterations and show her how I had changed the apron profile, she was so impressed that she did a tracing of it to use as a reference to the new pipe band kilt she had plans of making for herself, as she commonly has the same issues with the curling of the apron. It was very humbling to be sharing tips with the author of the amateur kiltmaker's bible!