I'll stick with pinning the seam line horizontally with fine pins making sure that only the tip of the pin is lined up with the seam just for the rare instance when I don't pull it out in time. Besides, it's far less annoying to pull pins out as I sew than to carefully unpile several feet of sewn fabric and retrieve a mess of pins before I can press what I just stitched.
I set a pin at the very end of the seam line and pull it out slowly at a slight upward angle to keep that last little bit of fabric from pulling to the left. Works every time. Enders work, too, but they're an extra step and extra thread.