The advertised footprint is pretty accurate on Marine Solutions website. I would also take a look at the MSX 160 over the Nw 200. I had a nw 150 and just replace it with the MSX 160.....there is no comparison.
THe nw 150 or 200's are great skimmers but, the MSX line is AWESOME. Just a way better designed skimmer, and the Sicce pumps are incredible.
Also wanted to add, the msx 160 is only $30 more than the nw 200 right now and you dont need to add gate valve or any other mods to get the mass airflow, like you do with the octo.