IMHO, 4G file size seems too small, my personal preference for terabyte size db's is 32G file size. We did have a terabyte db with 64G file size and had many issues with the backups (this was 10g).

Each expert will have it's own opinion about setting an "ideal" file size, but you may want to take into consideration the size of the physical cylinders/tracks/partitions of the raid array. On a SAN you would consider the size of the disk segments (logical partitions).

Good luck!