If you are having that much of a problem, as I often do,
here's one suggestion.
Start with the "test" method. Sew two 2.5" squares together, press to set your seam then press it open and measure your final product. It should measure 4.5" If it's not, adjust accordingly.
I haven't read through all the posts yet, so this might have already been mentioned, along with the all important PRESS, not IRON (moving iron back and forth).
Above all.........relax...check each block as you go along and BEFORE you sew it to another...as long as all your blocks are the same size all will turn out well. No kidding.
:lol: :thumbup: