It's not imperative. Actually, I think your best bet would be to put one of the shoulders on the 6's and use the 7 to knit--the needle you knit with determines the size of the stitches.
"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