If you're using 28ct fabric, I'd use 2 threads, dcondon. Just make sure your threads lie flat, parallel to each other and aren't twisted. That way you'll get the best coverage and the neatest looking stitches. Drop your needle periodically and let the thread untwist before continuing your stitching. You should be able to tell when you need to do that. Good luck, I love this pattern, so please post progress photos as you stitch it.

I just looked up for U the linen should be 32 c lamewoold and it take 22 floss no. of DMC for it I presume 2 plies are enough for this matterial. Have fun