I have some deep concerns regarding your use of used or worn clothing . Many years ago I had to line a dress for a daughter after only a few washings the lining frayed out and my work was in vain .I understand your need to be frugal but often the fabric does not have much left in it .I think your color choices are really great and sashing with cornerstones look good .It also stablizes the block so you do not have along run of sashing that can ripple on a new quilter. What you have done looks very accurate to me .Have fun and go for it.