We have a customer that builds ICF pools, 48"x8" walls without footings. We have tried a horizontal 2x4 at the top with a turnbuckle, and Fab-Form two rows of horizontal and verticals spaced about 6'. They still can't get the walls as straight as they would like. Suggestions?

I went from one side of the pool to the other. I screwed 2 foot square of OSB to the wall ties and then a vertical piece of 2x4 and then attach to the 2x4 your brace to the other side.