Thanks Kathy. I'm making a few swatches before a final decision so have been using cheapy left over yarn. I think you're right about needing something more dense.
Funny you say to try tightening tension in the chains a bit. So many of my problems are due to a tight tension, I think I may have overcompensated here! I thought maybe tightness in the chains was making them stand out from the crowd so I've been deliberately loosening them off. Think I'll change tactic over the next few rows and go tighter to see if that makes a difference.
Appreciate the help!