Could work.
Would be uncomfortable for people sitting in the back though if the speakers were angled, and if you had them sitting so they faced across the seats, the sound would just sorta die. It's a possibility though.
At the moment, I'm thinking 6x9's in boxes, sat on the parcel shelf, with some sort of connector plug so I can take the parcel shelf with the speakers out.
But if they were on the parcel shelf, which way to face them! I don't think straight ahead would do the sound much good. I'm thinking if they point at where the ceiling meets the windscreen, that'll give the best sound range.
