If your concern is getting the entire quilt, once quilted, onto the bar that's in the throat of the machine, I've done a quilt where I quilted as far as I could, then took it off, turned top to bottom, mounted the loose end of the backing to the bar in the throat region, layering the top and batting in the roll as I carefully wound up the unquilted portion to the take up bar.
Then I started to quilt from the already quilted part, which was on the belly bar up, checking for wrinkles and pleats each section before quilting.
Kind of reverse floating the top.
If my explanation is too difficult to make sense of, just PM me.