I have found that solar panels can be a bit tricky.
They are often high up, and if there is any flex in the pole it means that the clamps often catch the bottom of the panel. I use an slx-30, and could do with a gooseneck to take up the slack.
The good thing is that punters cant really see how well the job is done as they can't peer through them and whinge about spots.
The last ones I did were £5 per panel.