I removed the "top" rail from my LA. I've always floated my quilts and left the rail unused, but then always had to be tucking the top and batting under and it made it hard to adjust as I was working. I figured I needed it as it helped to add tension to the quilt, but then realized that I always loosened the quilt enough before quilting (my machine likes a rather loose quilt) and at that point it was doing nothing.
I fought with that rail for several years - and it is sure nice having it gone and the quilting is not affected by not having it there.