Mount it outside...
Although I'd bet it'd work almost anywhere, the key is to mount it as far from metal that'd interfere with it's ability to receive the transmissions from the GPS satellites as possible. Best is outside the pyramid of the stays & shrouds, like on a radar mast, or a stern pulpit. I once had an early Garmin handheld. I don't remember the model, as I returned it to West Marine, and bought a Magellan, which at the time worked marginally better -- now I use both manufacturers. It wouldn't locate itself unless I stood up on the transom, and held it at arm's length. Not really practical for ongoing VMG calcs when you're beating into the wind that's blowing 25 knots...
