My earlier coro creations were held together solely with hot glue. Many of those became brittle and parted in some sections after a year or two. My later creations were made similarly to djgra and tacked with hot glue and siliconed (same bunnings variety). None of my later creations done in this way have faltered, when using reasonable coro. I find 5mm coro the best to use. 3mm tends to become brittle after some time in the hot Aussie sun.