Holder für pool spotlight

I've bought two spotlights for our pool and I'd planned to fix them with a magnet. But I realized, they have been made from aluminium so I've designed a holder to fix them on the pool border.

Here are the spotlights on amazon:
https://www.amazon.de/gp/product/B07DK9NWT1/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I've added a second part, if your pool border is a little bit thinner, then you can use it to shorten the holder a bit - simply glue it on the needed side.