Does your Duster "float" at highway speed?

My car likes to wander a bit at speeds around 70mph. I had the alignment shop put in +5 degrees of camber which helped a bit. My front fenders and hood are fiberglass so I'm wondering if my front end is just light and that's the way it's going to be. My front tires are 235/40/18. Rear Tires: 245/50/18.