You can allocate an offset up to a factor of 10 so you should be able to do 2 servers x 4 outputs as one image easily. One server will be minus offsets to the left and the other positive offsets to the right. That way the centre of the image will be located at the join between Projectors 4 & 5.

The main thing will be running a network so you can sync one server to the other.

Cheers

Toby