If you provide a link to your block pattern we could give you a much more precise answer.
With pieced blocks you can calculate the size for on point placement along the edge, but it is a lot easier to make full blocks and cut them down, however, you can't get away with just 4. If you do this, you will loose the points along the edges of your quilt. The blocks need to be cut on the diagonal with an additional quarter inch past the edge to edge line. Also, these blocks will probably have bias edges, so it's best to stay stitch first.
Also, depending on your block pattern, you may be able to make partial blocks. Make one, stay stitch and cut. see if any of the individual patches lay entirely in the discarded portion. You can also make full blocks and sew the discarded portions together for another project.
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