Of course, using another magnet would do the trick. But the sensor cost £35-40, kind of want it to work 'out of the box' . I like the neat finish of the magnet band. I bought it with the trip 300. And for the price I might have gone in another direction if knowing it wouldn't set up properly.
I emailed Bontrager customer support and got a quick response. Stating they weren't aware of any problems at the moment. And that people were using the middle size magnet (as pictured by railgun.) And also they would get back to me after speaking to management in the U.S.