I typically use the 3 step zig-zag stitch found on my Brother machine.
I float my tops and have cut my batting a bit short several times. You'd think I would get it right after doing that once. When that happens, I have been known to butt up the new piece of batting and flip the quilt top over it and continue quilting. I use pantos that are medium density of stitching and Warm & Natural batting, which recommends stitching every 10 inches. As long as I have quilted enough stitches, the W&N doesn't move. When I say enough stitches, the panto patterns I typically use, are ones that don't have really straight lines along any edges, so the interlocking edges go back & forth over the batting I butted up. I haven't seen any separation in the batting, and between us and the dogs using the quilts, they get a lot of washing.
Years ago, I saw an article that recommending this butting up method - they started by layering the two pieces of batting together, then taking a rotary cutter and weaved a cutting line that wasn't straight, sorta like uneven scallops. Picture the batting looking like a big long piece not on top of each other, except where the two pieces are to be joined. This weaving of the cutting means you can use straight lines of stitching and still have both pieces caught with the same stitches. I'll see if I can find the article.
https://answers.yahoo.com/question/i...2184254AAginNr
http://quiltersbattinguniversity.blo...wo-pieces.html (I use this method but don't use the fusible to hold it together.)