Scarf Q - slip stitch

I was thinking about trying to do a stripy knitting scarf but the yarns I picked out half are light worsted and the others are heavy dk.
do you think if I double the dk I can do it that way - worsted on one side and dk on the other, sewn or knit together?
I can’t find any other yarns that are the right colors…
maybe I am kidding myself I could even do it if it was possible, but I would just like to know if theoretically it could happen even if it won’t for me.

also, does anyone know if slip stitch patterns use more yarn than normal knit-purl ones? or depends on the slip stitch?