I would do white thread and what I call the "pong" method. (If you don't know the computer game pong, a ball falls from the ceiling and you bounce it from a platform to hit targets.) This method only works with rectangular quilts, cannot be square.
Start at 1 corner, walking foot, 45 degree angle across the quilt until you get to the other side. Pong off the edge at another 45 angle, pong, pong pong across all the edges and you'll end up with a continuous diamond quilting (no breaking thread!) without putting a giant bulk of quilt under the harp....well the first line is a doozy but after that most of the quilt is on the left side. Very simple and very quick.
White thread because I don't get a super confident vibe off of your original message. Really you could do any color: a sand or grey eould be more visible but still neutral. A lovely pink or peach might coordinate with your blocks and provide a cohesive unifying element.
I'm sure this method has another name, but that's what I call it. Try it with a piece of paper (ordinary 8x 11) to watch it fill the space.