Good question Dave - I really hadn't considered it. Only about 5-6 inches of the drum are exposed. Also, I don't think these are fiberglass, but rather a very thick plastic or poly-something.
I've considered putting a few gallons of water in each drum to give it some stability and lower it in the water a bit. That would help reduce sun exposure too.
I'll email you a photo so you can see it.
Dave
