You can use whatever needle size suits your yarn that gives you the fabric you like. The main thing is to keep your strands loose so they don't pucker, which you already know, I'm sure.
Since stranded knitting is essentially doubled, a little looser stitch might keep the fabric from being stiff.
"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