Some folks here have used them to mount downrigger bases on their boats. I'll be doing that with my new 215 Chaos come the end of March.
Here is one of the threads discussing that. You can find more by using the "Super Search" at the bottom on the home page in the middle of the screen. Be sure to click on the "Go" button after entering your search request. If you just hit "enter" it won't work.
Cannon Easi Troll Downriggers