Mike is right, depending on how you're using your GPS. For the most part I found that while driving, looking at the GPS just made me drive bad. Let the crew handle looking at the GPS. We had tried strapping them to our legs into our harness leg straps. Worked for crew, not for me. Put it in a dry bag, hook the strap to your vest, either put it in a pocket or just drop it down inside the front of your vest.

Last year we mounted two Velocitek Speedpucks to the boom, one on each side. We used those for compass/heading or speed. They're big enough to see out on the wire, and for most of the sailing that's about all you need. I ended up velcro strapping my Garmin to the boom next to it, and set it to the big arrow screen and let it navigate through the waypoints put in. That display was big enough to see at a glance, gave me just enough to see where we were. If there was more I needed from the GPS I bugged Alex for it.