I did something similar for my 350, but used the foam backed tape to attach the 350 directly to the cover. Best Buy was selling the original 300 black covers for about $8 a few weeks ago, so I picked up one. I just removed the plastic holder and didn't reuse it.

I'm not sure I would trust the plastic holder that had been cut in two and reattached by foam tape to hold my 350 in place. It probably needs better reinforcement and a stronger adhesive. But hopefully you won't have an accident with it.

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