Long arm quilting and spray baste
 

I have a finished pieced quilt top, the back and batting have already been spray basted. Can I load the back and batting on the long arm frame and then float the top to long arm quilt it? I'm thinking it should work but would like to know before I screw it up.

I don't see any reason why you can't do it. I have a LA with a 10ft frame - never really thought about spray basting the batting on, just attach the backing, lay the batting over and stitch it down.

When you roll the backing/batting onto the front roller, I would keep it a little looser than usual. Every time you advance the quilt, flip the top up and examine the new section of batting & backing, smoothing it if needed.

What PaperPrincess said....and keep an eye on your needle. The long arm needle moves so much faster (as a rule), than a domestic machine. You might need to clean it off occasionally off the needle if it picks up some of the spray basting. I would unthread the eye and wipe the needle with rubbing alcohol...maybe when I change the bobbin...and of COURSE not over the quilt. (I only say that as that is something I might do. I get squirrelly like that sometimes!)