Back in the 70s we were always looking for the next best 8 track player. For that reason we often connected the wiring and never actually mounted the unit to the dash. I remember applying the brakes and the player would slide out from under my seat. When I accelerated it would slide back under the seat. Matchbooks were also used as shims to make sure the tape would ride properly over the playback heads.
...if you're not into the whole brevity thing...