I too am a spray baste fan (all sizes of quilt), but I will pin or tack around the outside edge of a large quilt to stop it peeling back with all the handling.
I machine quilt on a domestic machine (Bernina 630, love it!), if I'm quilting continuous rows (like on a long arm) I will start at the edge of the middle row, and then work out towards the sides of the quilt. If I'm quilting motifs I'll start in the middle and work out towards the edges. I always do the borders last, sometimes after I've bound the quilt, though this does give you less to hold onto. I can't remember now why I did this the first time, but I must have had a good reason