I made a queen size quilt (Star Wars) for my grandson, and it, too, felt heavy even before quilting. I used Soft n' Bright (polyester), 1/8" thick, by The Warm Company. (I think it is also available as 1/4"). Based on my experience, I believe this would be the perfect batting for your project. This batting is available at Joann's as a pre-cut 45"X60" package or 90" width on the roll. I usually just have them cut what I need.