Just for terminology's sake, what you have is a circular needle. A cable needle is a short needle used to hold stitches to make cable in knitting. Not a big deal. Anyway, knitting large objects back and forth on circular needles is extremely common. Sometimes the number of stitches just don't fit across a regular straight needle.
So you're idea is exactly the way to make something that big. Good luck with it!
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry