another.
it sounds like you trimmed the corners off blocks, thinking you would then sew them onto different blocks. what measurements did you use, when cutting the corners off? did you cut a full 2.5" in from the corner, or some other measurement? (i'm trying to figure out if the 2.5" squares are still useful to you).
if you cut at 2.5", then i think the only way to rescue this is going to be to trim your blocks. sew the corners on as you have been doing, then carefully trim it square again. you should end up with a 7" block i think. the pattern will still work, but your quilt 