'Just playing 2 layers of uncompressed...' is going to overload most discs....even possibly your raptor raid.
headline data transfer rates are NOT useful indicators of whether it will work or not.


if it cant keep the movies together by starting playback at the same time. it wont work anyway you do it.

you need to start play at same time.

and see what happens - if they drift the computer and disc system cannot keep up....so you cant do it.....