keeping straight edge w/dif. yarn weights

[anita_barcolounger]

Hi knitters! Thanks, Amy for such a great site - I've learned so much!

I have two questions - and appreciate anyone who takes the time to read & answer.

Here is a picture of a test piece for a scarf I'd like to make for my niece. I'm knitting with 2 yarns together - a very lightweight lavender eyelash throughout, and combining that with a different yarn every inch or so.

One of the yarns is Caron Fling (in middle & top), which is a chenille noodle eyelash yarn. Because it's thicker, it bumps out the edge. I'm using all poly and poly/acrylic yarns. Can I even this out with blocking, or would it be better to decrease for that yarn? I tried a smaller needle and so far no luck.

Also, if I am rotating 4 yarns randomly for the stripes, should I carry them through (like a striped sock?) or cut them & weave in all the ends?

Thanks again!