Bend the tabs on top upwards, the tabs at the bottom downwards. Can't see a reason why you couldn't use the side tabs too - I'm assuming that the cradle fits snugly into the the opening in the panel?

No need to go to 90 degrees, it's enough to get them down enough so that they rest against the backside of the panel. My tabs are probably only bent between 30 and 45 degrees.

You should be able to see, through the cut-outs around the tabs, where the back edge of the panel is, and get the best placed tabs down so that the press against the back of the panel.

Quick and crude drawing attached. Left part is cradle and plastic (black) seen from above/below and right part is bottom of cradle seen from the side

Edit: I also bent the tabs after inserting the cradle (only way possible unless you dismantle the entire dash)

HTH,

/Michael