Yes, it's possible to get a good stitch, but I concur with Hans in that the location was not well chosen for assessing the setup of the panohead. Even so, the one thing that would have helped to reveal parallax (the nearest upright post in the fence) is bang in the centre of an image and not in either overlap. It is possible to see significant verical parallax between the rail and the far background by examining seams between upper and lower row images in a PSD o/p. This amounts to a shift of about 14 pixels at full image size, so is far from negligible. More distant features show minor horizontal parallax shift, so I would say that the panohead setup could be improved.