The most important aspect is to keep the bit rate below 15Mbps for a movie. Any time you have a bit rate higher than that it forces the HDD to do multiple read cycles for a single frame.
In other words, when you are thinking about really high res files for use with the Collage system you have to keep the overall resolution down to the point that you aren't exceeding 15Mbps when playing the movie.
The most important aspect is to keep the bit rate below 15Mbps for a movie. Any time you have a bit rate higher than that it forces the HDD to do multiple read cycles for a single frame.
In other words, when you are thinking about really high res files for use with the Collage system you have to keep the overall resolution down to the point that you aren't exceeding 15Mbps when playing the movie.