I DO NOT have a Forerunner 305...so your experience will definitely vary.

I have the Forerunner 405, and used it for cycling until I got a Garmin Edge 500. One of the things that I hated about the 405 was the way it sat on my wrist. I've got large wrists and it was just uncomfortable with its built in curvature.

So, I got the replacement strap pictured in the second link (shown below)


This made the 405 much more comfortable. I used that for a month or so and was very happy with it...other than needing to look at my wrist while riding. So I bought the mount in the first link. It works GREAT. You don't need to use the zip ties, so you can move it from one bike to another. The watch strap wraps around it quickly and securely, and the tightening of the strap causes it to grip the handlebars nicely.

One thing to note. If you use a watch strap that is a 'pin and buckle' type (as opposed to a velcro strap like the one pictured), then it might be more difficult to put it on the mount. Not much more difficult, but if you're trying to save time in a transition, it's something to think about.

Charles