I was thinking of a general Trilogy boxset cover for a 3-disc box, in the same style as above - which is the same size as a normal single disc box.
There was a really great guide with templates for the differing types and sizes of dvd boxes (+ discart and inserts) somwhere here on the ot.com, but I just can't find it anymore
*** edit *** - a decent cd/dvd template website is here, though sadly none for the larger 4disc box sets and larger:-
http://www.diskfaktory.com/dfshare/info/ArtworkTemplates.asp
Measurements for covers to fit a...
4-disc box set are - 281mm wide, 185mm high, with a spine width of 20mm - 3325 x 2188 pixels at 300dpi
6-disc box set are - 288mm wide, 185mm high, with a spine width of 27mm - 3402 x 2223 pixels at 300dpi
