| For a yoke mount some cable ties will help of put some sort of draught excluder type padding between the timer and yoke. I wouldn't just rely on Velcro on the yoke, no way would you want the thing coming loose.
In stealth mode under the seat make sure its not getting too hot and that includes the wire run to the sensor.
The sensor should be OK with velcro if its not in any strong wind blast and if you cable tie the sensor cable to somenthing then even if it did let go the sensor won't go far.
Ray. | 
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