For exactly why the last post said he got it to stay between the gauges with tension ....
I didn't want the gauges crushing the display and taking off the cover gives it a flatter place to mount that sits lower between the gauges and doesn't get squished. It's only plastic and putting pressure on it can't be good for it or the gauges in the long term, especially in the sun. You can mount it there, cut and shape your own piece of aluminum for a bracket, buy a clock mount and adapt it, or spend 150 euro's for a beautifully made German enclosure.
Those are the choices I've seen.