You do indeed. This is why it took me so long to sort this as i was looking for a good way to fix without drilling. These seem fine, with 20kg pull each the panel is pretty much rock solid. I wanted to get the panels as low profile to the roof as possible to try to avoid wind issues, and these sit under the height of the mushrooms. Time will tell of course if these turn out to be viable and I'll probably be sweating when its windy, but early signs are good. Note my roof is 'smooth' so this helps!