The trick for you would be not to cut the larger piece. Use that as your guide because that is the final size it needs to be. You might have to sew a smiggen over from the line. Having said that, if you always seem to have problems, I would suggest purchasing the Triangulation 3.0 CD. It cost about $30 but has paper piecing patterns for every size possible for half square triangle, flying geese, etc. (you will need a printer). Every time you make one of these units, they would be perfect. Good luck.