we rebent the brackets on mine into like a z shape to drop the height and rotated them so they didnt sit in the factory mounting holes. Tacked them down with a dab of silicone where the mount touched the dash pad. Had to cut a piece out of the speaker cover too, its only held in by 2/3 clips now. They won't go anywhere, we played with them for a while.
this was for my cutlass... might be a bit different in the regal. Sorry, I should have taken pictures. I'll try to re-explain if it didn't make sense.