Wendy, if you like the diagonal design I really hope you will go for it! Just be careful not to stretch the fabric as you sew, and do more than the minimum quilting! If I were doing this, I would definitely choose the diagonal lines and would stitch along every natural division.
YOU CAN DO THIS!!
I have never spray basted a quilt, so I can't say how it works for me, but a lot of people really do like it. I have always pin basted quilts that I finish on my domestic machine by taping the backing securely to the vinyl floor in my sewing room., smoothing out the batting (which I have tumbled in a hot dryer for a few minutes with a wet hand towel to remove the wrinkles) and pin basted close enough that I can't put my hand anywhere on the quilt without touching at least 2 pins. I did it this way for years, but now I mostly quilt with my long-arm, so I don't often get on the floor for that process any more.
Did you know that a long-armer can baste your quilt for you? Ask him/her to stitch horizontal basting lines about 4" apart with VANISH thread, and when you wash it those stitching lines will all just disappear! No worry about shifting and no pins to deal with!