LTJ: What kind of Toyota? (I ask because I'm considering a New Prius, and I intend taking it to Cambridge Car Audio)

My Peugeot install (for the last 2½ years) is at about 30° downwards (i.e. too much the right way, the same as you describe but less extreme). I have had one Fujitsu drive fail, but I don't think the install angle was a contributory factor. And the other (IBM) drives that are or have been in it have been faultless.