Wow! thanks for all the food for thought! this board is amazing!
I decided to do cross hatch with invisible thread measured 3 inches apart. I tried the marker but it disappeared before I could sew it so I used tape.
The L shaped attachment for my machine only goes to 2 or 2.5 inches.... So far I am about 35% done with the first set of diagonals. I'm not totally sure if I am going to the crosses or just the single diagonal. I still feel like I'm fighting the quilt here and there.