I also have an Innova. I haven't used 2 batts, but I'm confused by your question about the bars. I always float the batting, would never put it on a bar, but maybe that's not what your question meant anyway. I float the top of the quilt top, and lately I have been floating the bottom of the quilt top as well, although sometimes I do roll it. With the Innova there's no problem keeping the batting smooth, since with each roll of the quilt you can lift the front bar (assuming you're using it) and smooth out the batting, remove any excess threads from the underside of the top, etc.
I started out using W&N for every quilt, but lately I have been using Warm & Bright, which is a poly batting made by the Warm Company (makers of W&N) and I really like it! It gives great definition to the stitches and is very smooth and even, unlike some poly battings.