I'm not too worried about NES carts (unless the specs offered on site is way off), but I am concerned about SNES cart size. The thickness of an SNES cart is 0.8" and the case outside dimension is 0.8" so I don't think there would be adequate room for a SNES cart, but I hope I can squeeze it in there.
Measured the carts (W*H*T in millimeters. Divide with 25.4 to get inches)
NES carts are 0.62 inches thick (134*119*16), so tight fit that too, especially with manual.
SNES EU/AU/JAP carts are
SNES US carts are 0.78 inches (138*86*20mm)
As for the manuals I haven't given thought about it, and it seems unlikely I could fit SNES/N64 manuals in there (nes I don't think there would be a problem).
For this I have another topic:
http://www.thecoverproject.net/forums/index.php?topic=4481.0Small (IE normal) NES manuals no problem, but the bigger NES manuals are the same size as SNES/N64.
Those fit nicely into DVD cases or folders like mty nes manuals.
I have bought folder pages for those too, no pictures of those yet though.