Have you ever heard of Sharon Schamber? She has the best long arm quilting ideas. I like to watch her on You tube. Just go to youtube.com and search for Sharon Schamber and you will find several videos of hers. My favorite is how to make leader with velcro.
I made the leaders she sugguested using velcro that attach to the leader you already have. You don't need to pin the back but sew it to the leaders. You would need to look at you tube to see exactly what I mean. There are several different videos to watch concerning leaders. Need to watch them all as each one adds something different.
Also, she tells how to float the top by basting it to the on top of the batting & backing. I believe you will find that on the video on how to baste a quilt. I use this basting method and it works very well for me.
Hope this webb site helps you, Sharon is a very good teacher of long arm quilting