AMG I could scan a picture of the latest pipe I got smashed that would help verify that theory (seiki efra). The dent is where you described and shaped how you described. I took a ram by a serpent impulse (as I was lapping his butt last week) and my pipe got filleted.
I did notice from experimenting with these pipes that the lip on the X12 is larger in diameter than other pipes and makes a tighter seal w/ even the larger couplers.