What is the update on your pieces??When I hand piece...I look straight down on the corners and sew an actual 'x' thru them on the corners.
If you not exact on your seam allowance...it will mess w/you like this:)I had a great and helpful hint to marking your lines exact.....!!
Use and index card...the lines on it are the exact seam allowance! It works...Keep us posted..Skeat