I had issues with some store bought hooks that were very tight and didn't survive well being exposed to UV. I designed these to be printed with PETG for UV resistance, and to be simple to put in place while balancing on a ladder. They've held up nicely for weeks now even in windy weather!

Print many of them at a time lying down on the bed. I think I went with 2 perimeters and a pretty high infill, but they're not very large so wouldn't make much of a difference. PETG or other similar materials for UV resistance recommended!  These can probably be scaled down a bit to get a slightly tighter fit if you want to.

Update: Some of these I printed have now been up for 9 months at our house, using a no-name roll of black PETG, and are still doing great!

Second update: still looks perfectly fine after 13 months!