Thanks everyone!
Very weird about the KB61 gigbag...
Dimensions of the PC3K6: 100 x 35.5 x 12.3
and the inner dimensions of the bag: 96 x 36 x 10 cm
http://www.thomann.de/gb/kurzweil_kb61_gigbag.htm
"Kurzweil KB61 Gigbag, Softcase built for devices with 61 keys, for PC361, PC161, K2661, K2000, KME61 and other,"