Depends how often you plan to wash it. There are 2 things to consider when choosing quilting distance: whether the batting will migrate, and whether the fabric & stitching will hold up. I used to only worry about the first until I saw that maybe 6-7 years later, my quilts had to be repaired. From what I've learned since about cotton fibers, stitching should be no farther than 2" apart. So that's what I now aim for as the farthest apart I quilt.
Assuming you only do straight line quilting, there are options other than cross hatch that would work. You could do a square within a square design an inch inside (that's what I'd do -- going around the square & then continuous line to the next square). Or do a couple of diagonal lines through it in the same direction 2" apart.
btw -- Fairfield makes Soft n Crafty & recommends quilting every 2-4". Based purely on batting, I think you should be fine at 4.5".