The digital clock text is always shown in the horizontal, even when the panel is displayed on the vertical orientation. In this case the panel may have to be too large to read the clock information. It would be nice if the digital clock text could be displayed on the same panel orientation. Please, add the option "Rotate clock in vertical panel", similar to the "Rotate buttons in vertical panel" that already exists for the WindowButtons pluggin.
There are TWO vertical orientations, of course. So, a "rotate clock..." checkbox was provided, it would *not* fully answer the problem. We would need *both* a right and a left vertical orientation. Between Xfce 4.6 and 4.8, the Panel Properties *reduced* the ways to specify these particulars of the orientation. They used to have a box that let you select from all of 8 qualitatively different positions. And when the panel was on the left-side (vertical), the Windows Buttons had their "up" facing left, and flipped when on the right. The window buttons orientation is broken in 4.8 for vertical panels on the left side of the screen.
The whole panel is rotated consistently, and the clock plugin along with the rest.